
Class _/ 



Book_r: 



tLz. 



Copyright )J^_ 



f/6 



COPYRrCHT DEPOSm 



ELECTRIC 
RAILWAY ENGINEERING 



qiMli Mlllll lllililMlilillllll^ ■■■illllllililillll^ 



I McGraw-Hill BookComparry^ | 

Pu6Cis/iers qf3oo^/b7' 

ElGCtiical World TheLnginGering andMining Journal 
LngiaGering Record Engineering Novv^s 

Kaiiw^A^e Gazette American Machinist 

Signal Lnginpor . American Eng^inea* 

Electric Railway Journal Coal Age 

Metallurgical and Chem ical Engineering P o we r 



ELECTRIC 
RAILWAY ENGINEERING 



C. FRANCIS HARDING, E. E. 

PROFESSOR, ELECTRICAL EXGIXEERIXG; DIRECTOR, ELECTRICAL LABORATORIES, PURDUE 

university; fellow AMERICAX institute ELECTRICAL ENGINEERS; ASSOCIATE 

AMERICAN ELECTRIC RAILWAY ASSOCIATION; MEMBER SOCIETY FOR 

PROMOTION OF ENGINEERING EDUCATION; NATIONAL ELECTRIC 

LIGHT ASSOCIATION, ETC. 

ASSISTED BY 

DRESSEL D. EWING, E. E., M. E. 

ASSISTANT PROFESSOR, ELECTRICAL ENGINEERING, PURDUE UNIVERSITY; MEMBER AMERI- 
CAN INSTITUTE ELECTRICAL ENGINEERS; ASSOCIATE AMERICAN ELECTRIC 
RAILWAY association; MEMBER SOCIETY FOR PROMOTION 
OF ENGINEERING EDUCATION 



Second Edition 
Fully Revised, Enlarged and Reset 



McGRAW-HILL BOOK COMPANY, Inc. 
239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 

1916 




^^' 






Copyright, 1911 and 1916, by the 
McGraw-Hill Book Company, Inc. 








/-r 




4 



ip- 



T H K M A r« L TO PRESS YORK PA 

©CU420413 

"7^ ^/ > 



? 



V\ 



PREFACE TO SECOND EDITION 

A most gratifying reception of the three impressions of the 
first edition of this text by the large number of technical institu- 
tions in which it has been adopted, and the rapid development 
of electric traction during the last few years, warrant a second 
edition. 

Although but one entirely new chapter, that entitled ''Loco- 
motive Train Haulage," has been added, practically every 
chapter in the book has been completely revised and further 
illustrated. Tabulated data representing actual operating 
conditions in railway practice have been increased by 50 per 
cent, and more than 50 illustrations have been added. 

The author has been very ably assisted in this revision by 
Professor D. D. Ewing, also of Purdue University, whose experi- 
ence with both steam railroads and electrification projects has 
well fitted him to discuss the problems of heavy electric traction 
which have been especially augmented in this edition. 

This opportunity is also taken to express appreciation of the 
assistance given by Mr. E. A. Bureau, graduate student in 
electrical engineering at Purdue University, whose research re- 
vealed many of the advancements in the profession which have 
been incorporated in this volume. 

It is hoped that the new edition will prove its added worth to 
both the educators and railway executives whom the book has 
been privileged to serve in the past, and that in addition its 
field of usefulness may be broadened by its more thorough treat- 
ment of this rapidly advancing profession. 

C. F. H. 

LaFayette, IXD. 
December, 1915. 



PREFACE TO FIRST EDITION 

To students in technical universities who wish to speciahze 
in the subject of electrical railway engineering and to those who 
understand the fundamental principles of electrical engineering 
and are interested in their application to electric railway practice 
it is hoped that this book may be of value. 

While it is planned primarily for a senior elective course in a 
technical university, it does not involve higher mathematics 
and should therefore be easily understood by the undergraduate 
reader. 

The volume does not purport to present any great amount of 
new material nor principles, but it does gather in convenient form 
present day theory and practice in all important branches of 
electric railway engineering. 

No apology is deemed necessary for the frequent quotations 
from technical papers and publications in engineering periodicals, 
for it is only from the authorities and specialists in particular 
phases of the profession that the most valuable information can 
be obtained, and it is believed that a thorough and unprejudiced 
summary of the best that has been written upon the various 
aspects of the subject will be most welcome when thus combined 
into a single volume. 

The author wishes to express his appreciation of the assistance 
of Mr. Emrick, instructor in electrical engineering at Purdue 
University, in preparing illustrations for the book and to those 
students who by thesis investigations have added to its value. 

LaFayette, IXD. 

September, 1911. 



CONTENTS 

Page 
Preface v 

PART I 

PRINCIPLES OF TRAIN OPERATION 
CHAPTER I 

History of Electric Traction 3 

CHAPTER II 

Traffic Studies (Predetermined) 13 

Population — Growth in Population — Riding Habit — Competition 
— Gross Income — Number and Capacity of Cars. 

CHAPTER III 
Traffic Studies (Existing) 25 

CHAPTER IV 
Train Schedules 31 

CHAPTER V 

Motor Characteristics 37 

Motor Characteristics — Prony Brake Test — Pumping Back Test — 
Test Using One Motor as a Generator — Gear Ratio. 

CHAPTER VI 

Speed Time Curves (Components) 49 

Weight of Car — Bearing and RoUing Friction — Air Resistance — 
Rotative Inertia of Wheels and Armature — Grades — Curves. 

CHAPTER VII 

Speed Time Curves (Theory) 59 

Coasting — Braking . 

CHAPTER VIII 

Distance, Current and Power Time Curves (Theory) 66 

Distance Time Curves — Current Time Curve — Power Time Curve. 

xi 



Xll • CONTENTS 

CHAPTER IX 

Page 
Speed Distance, Current and Power Curves (Concrete Examples) . 71 
Speed and Distance Curves for Actual Grades — Current and 
Power Curves. 

CHAPTER X 

Speed Time Curves (Straight Line) 80 

Energy Calculations — Energy During the Braking Period — 
Coasting Energy and Train Resistance. 

CHAPTER XI 

Locomotive Train Haulage 89 

Drawbar Pull — Power Required for Train Haulage — Deter- 
mination of the Tonnage Rating of a Locomotive — Determination 
of the Locomotive Capacity Required for a Given Train — Speed, 
Distance, Current and Power Time Curves — Concrete Example 
of Speed, Distance Current and Power Time Curves and Motor 
Heating Calculations — Regenerative Braking. 

PART II 

POWER GENERATION AND DISTRIBUTION 

CHAPTER XII 

Substation and Power Station Load Curves 102 

Load Factor. 

CHAPTER XIII 

Distribution System 106 

City Systems — Financial Considerations — Types of Systems — 
Bracket and Span Construction — The Third Rail — Catenary. 

CHAPTER XIV 

Substation Location and Design 120 

Substation Location — Substation Design — Synchronous Converter 
— Methods of Starting Converters — Transformers — Motor Gen- 
erator vs. Converter — Switchboard — Storage Battery Auxiliary — 
Arrangement of Apparatus — Wiring — Lightning Protection — Por- 
table Substations — High Voltage Direct Current Substations — 
Single-phase Alternating Current Substations — Outdoor Substa- 
tions — Substation Cost. 

CHAPTER XV 

Transmission System 149 

Mechanical Strength — Electrical Considerations — Voltage Deter- 
mination — Regulation — Capacity Effect. 



CONTENTS XlU 

CHAPTER XVI 

Page 

Power Station Location and Design 162 

Location — Design — Capacity — Choice of Prime Movers — Steam 
Turbine — Steam Engine — D. C. Generators — Polyphase A. C. 
Generators — Rating — Generators for Single-phase Traction — 
Transformers — Switchboard — Exciters — Arrangement of Equip- 
ment — Cost of Power Station Equipped. 

CHAPTER XVII 

Bonds and Bonding 188 

Compressed Terminal Bonds — Soldered or Brazed Bonds — Elec- 
trically Welded Bonds — Amalgam Bonds — Cast Welded Joint — 
Thermit Welded Joint — Electric Welded Joint — Bond Testing — 
Cross Bonding. 

CHAPTER XVIII 

Electrolysis 196 

PART III 
EQUIPMENT 

CHAPTER XIX 

Signal and Dispatching Systems 209 

Signal Systems — Block Signals — Manual Control Block System — 
Controlled Manual Block — Dispatcher's Control Systems — Inter- 
mittent Control Signals — Steam Railroad Practice — Track Circuit 
Block Signals — Block Signals for Alternating Current Roads — 
Single-track Signaling — Cab Signals — Automatic Train Stops — 
Cost. 

CHAPTER XX 

Track Layout and Construction 231 

Right-of-way — Trestles — Ballast — Ties — Rails — Specifications for 
Open Hearth Steel Girder and High T Rails — Rails of Steel Alloys 
— Rail Joints — Rail Corrugation — Roadbed Construction — Pave- 
ment — Special Work — Estimates. 

CHAPTER XXI 

Cars 253 

Car Selection — Car Bodies — Trucks — Motor Equipment — Light- 
ing — Car Heating and Ventilation — Current Collection — Car 
Wiring — Special Types of Cars — Pay-as-you-Enter Cars — City 
Cars — Suburban Cars — Interurban Cars — Elevated and Subway 
Cars — Freight Cars — Storage Battery Cars. 



xiv CONTENTS 

CHAPTER XXII 

Page 

Motors 275 

Direct Current Motor — Commutating Pole Motor— Field Control 
Motors — Pressed Steel Motors — Single-phase Motors — Adapta- 
tion of the Direct Current Series Motor — Adaptation of Induction 
Motor — Construction of the Single-phase Motor — Characteristics 
— Operation on Direct Current — Repulsion Motor — Induction 
Motor — Frequency — Motor Design — Rating — Motor Selection — 
Selection of Motor for Specified Service — Selection by Comparison 
— Effective Current Method — Method Proposed by Armstrong — 
Method Proposed by Storer — Method Proposed by Hutchinson — 
Regeneration of Energy. 

CHAPTER XXIII 

Control Systems 299 

Types of Control — Main Circuit Control — Rheostatic Control — 
Series-parallel Control — Master Control — Multiple Unit Control — 
Electro-magnetic Control — Electro-pneumatic Control — Westing- 
house PK Control — High Voltage Direct Current Control Systems 
— Alternating Current Control — Combined Alternating and Direct 
Current Control — Regenerative Braking — Controller Selection. 

CHAPTER XXIV 

Brakes 318 

Coefficient of Friction — Braking Forces — Braking Equipment — 
Brake Rigging — Straight Air Brake Equipment — Emergency 
Straight Air Sj^stem — Automatic Air Brake Equipment — Quick 
Action Automatic System — Friction Disc, Electric and Track 
Brakes — Reversal of Motors — Motors used as Generators — Re- 
generative Braking — Brake Tests. 

CHAPTER XXV 

Car House Design 336 

Location — ^Layout of Tracks — Transfer Table — Building Design — 
Fire Protection — Pit Construction — Heating — Floors — Lighting — 
Offices and Employees' Quarters — Repair Shops. 

CHAPTER XXVI 

Electric Locomotives 346 

Advantage of Locomotives over Motor Cars — ^Locomotive Ratings 
— Locomotive Data — Modern Electric Locomotives — Split-phase 
Locomotive — Mercury Vapor Rectifier Locomotive — Design Re- 
quirements — Motor Mountings and Transmissions — Locomotive 
Weights — Drive Wheels — Trucks — Cab Underframing — Cabs — 
Riding Qualities — Costs. 



CONTENTS XV 

PART IV 

TYPES OF SYSTEMS 

CHAPTER XXVII 

Page 

Alternating Current vs. Direct Current Traction 369 

Electric Systems — Direct Current System — Single-phase System — 
Three-phase System — Combined Systems — Comparison of Sys- 
tems — Power Station — Transmission Lines — Substation — Distri- 
bution System — Motors — Rolling Stock — Power Factor — Fre- 
quency — First Cost, Maintenance and Operating Expense. 

CHAPTER XXVIII 

Electric Traction on Trunk Lines 387 

Frequency of Service — Speed — Comfort of Passengers — Safety — 
Reliability of Service — Increased Capacity of Line — Frequency 
of Stops — Improvement of Service — Tractive Effort and Drawbar 
Pull — Tonnage Ratings and Service Capacities — Accelerating 
Qualities — General Suitability for the Service — Electrification 
Increases Real Estate Values — Cost of Electrification and Opera- 
tion, 

Index 411 



PART I 

PRINCIPLES OF TRAIN 
OPERATION 



CHAPTER I 
HISTORY OF ELECTRIC TRACTION 

Although it is not the purpose of this treatise to relate facts, 
but rather to study the engineering and economic problems en- 
countered in electric traction, yet it seems advisable to review 
briefly the history of the development of the electric railway by 
way of introduction. 

Two distinct epochs were encountered in the brief period in 
which electric traction has come to the front. The first was that 
in which the experimental designs were hardly more than models 
operated with primary batteries. Occasionally during this 
period, however, enthusiasts who did not realize the insuperable 
financial drawbacks of primary battery operation constructed and 
experimented with cars of considerable size operated in that 
manner. Such was the car constructed by Page in 1851 for the 
Washington and Baltimore Railroad, which made use of a 16 hp. 
motor supplied with power from two large Grove cells made 
up of platinum plates 11 in. square. This first epoch was soon 
brought to a close, however, partly by the foresight of the inves- 
tigators who realized the limitations of the primary battery 
and partly by the failure of all attempts to commercialize the 
primary battery car by those who had continued to experiment 
therewith. 

The second epoch opened, after a brief interval of inactivity, 
simultaneously with the development of the reversible dynamo. 
In the development of this machine progressive experimenters 
could foresee the beginnings of electric traction upon a practical 
basis. Bearing in mind the existence of these two periods, the 
history of electric traction will be considered, greatly abstracted 
but as nearly as possible in chronological order. 

Since electric traction has ever been dependent upon the elec- 
tric motor and the latter upon the discovery by Faraday, in 1821, 
that electricity could be made to produce mechanical motion, 
the latter date rather indirectly and vaguely marks the birth of 
the subject under consideration. America has the honor of first 

3 



4 ELECTRIC RAILWAY ENGINEERING 

applying the electric motor to a car, model though it was, while 
later developments vibrated from America to Europe and back to 
America with a rapidity difficult to follow with accuracy. A poor 
blacksmith of Brandon, Vt., by the name of Thomas Davenport, 
has the honor of first making this application of an electric motor to 
a car in 1835, the motor having been constructed by him several 
years previous. During the short period of 6 years it is said that 
Davenport constructed over 100 electric motors of various de- 
signs. That which was described as having been exhibited by 
him upon a car at Springfield and Boston, Mass., consisted of a 
revolving commutated magnet which was caused to attract sta- 
tionary armatures arranged around the periphery of its path of 
revolution. The car thus equipped was operated upon a small 
circular track. 

About the year 1838 Robert Davidson of Aberdeen, Scotland, 
built a much larger motor placed upon a battery car 16 ft. by 

5 ft. in dimensions of the gauge then standard and operated same 
with 40 cells of battery consisting of iron and amalgamated zinc 
plates immersed in dilute sulphuric acid. It is of interest to 
note that after several successful trips over Scotland railways this 
car was purposely wrecked by steam railway engineers who 
were afraid it would supersede types in use at that time. 

Two rather fundamental patents were issued in England about 
this time, one in 1840 to Henry Pinkus involving the use of 
the rails for current conductors and another in 1855 to Swear 
which, although applied to telegraphic communication with 
moving trains, comprised the basis of the present current collect- 
ing trolley. Patents were also granted in 1855 by both France 
and Austria to Major Alexander Bessolo which covered the same 
fundamental principles but which described more in detail the 
third rail conductor, the insulated trolley, and even suggested 
central station supply. 

The experimental work in this country of Prof. Moses G. 
Farmer in 1847 and Thomas Hall in 1850 might be considered 
in particular because of the use for the first time of the rail as a 
conductor and the adoption of a geared speed reduction be- 
tween motors and driving axle. The work of Page, previously 
noted, deserves prominent mention at this time. For many 
years after these experiments, investigations in electric trac- 
tion seemed to be dormant, largely due to the general 



HISTORY OF ELECTRIC TRACTION 5 

realization of the impracticability of the battery as a source 
of energy. 

The second era of electrical railway development opened about 
the year 1861 when Pacinotti invented the reversible continuous 
current dynamo. From this invention may be said to have arisen 
all modern generators and motors. While these were gradually 
developed by Gramme and Siemens, Wheatstone and Varley, 
Farmer and Rowland, Hefner-Alteneck and others, Wheatstone 
and Siemens having almost simultaneously developed self-excit- 
ing generators equipped with shunt and series windings, re- 
spectively, yet a considerable period of time elapsed before these 
developments were effectively applied to traction. 

The work of George F. Green, a poor mechanic of Kalamazoo, 
Mich., has been quoted as the connecting link between the two 
eras. Although he began his experiments as late as 1875, after 
the development of the dynamo, his first model road reverted to 
the battery delivering current to the car over the operating rails. 
Although Green proposed the trolley for his experimental track, 
he did not make use of it. The following work of this man is 
rather pathetic, in that he constructed a car about the year 1878 
large enough for two people and realized the advantages of the 
dynamo for supplying energy for same. He did not understand 
how to construct this machine himself, however, and was not 
financially able to procure one of the few being constructed 
abroad at that time. He applied, in 1879, for patents which 
would probably have been of considerable value at that time, but 
because of limited funds and the fact that he was obliged to act 
as his own patent attorney, his claim was rejected and only 
finally granted in the year 1891 after a belated appeal to the cir- 
cuit court of the District of Columbia. 

The first electric road operating on a practical scale was the 
one exhibited by Siemens and Halske at the Berlin Exposition in 
1879. This consisted of an oval track about }i ^^^ ^^ length 
upon which an electric locomotive was operated with three 
small trailers accommodating from 18 to 20 passengers. The 
motor was mounted with its axle lengthwise of the car and 
power was transmitted to the car axle through a double bevel 
gear speed reduction. A speed of about 8 miles per hour was 
attained. The current was supplied by means of a third rail 
located between the running rails. 

The year 1880 in Europe marked the exhibition of another 



6 ELECTRIC RAILWAY ENGINEERING 

model electric railway at Vienna by Egger which used the running 
rails for conductors. In this year, also, the study of a method of 
replacing the pneumatic dispatch system of Paris by miniature 
electrically propelled carriages was carried on. Siemens pro- 
posed at this time a commercial road for Berlin and endeavored 
to obtain a franchise for same. 

The first electric road to be installed apart from an exposition 
was that at Lichterfelde, near Berlin, which was opened in 1881. 
A single motor car using cable drive between motors and axles 
operated upon this road, which was 13^^ miles in length, at a 
speed of about 30 miles per hour. It was sufficiently large to 
accommodate 36 passengers. Although a third rail road when 
installed, it was changed over 12 years later to a double trolley 
system. This road has remained in continuous operation. 
During this year, also, the horse railroad between Charlottenburg 
and Spandau was changed to electric traction. 

At the Paris exposition of 1881, Siemens and Halske demon- 
strated the use of the overhead trolley for current distribution 
to cars, the conductors consisting of metal tubes slotted on the 
underside, mounted upon wooden insulators, in which tubes 
metal contactors, electrically connected with the car, were 
allowed to slide. In 1883, a 6 mile third rail road was opened at 
Portrush, Ireland, which was worthy of note because of its 
operation from a central station driven by water power. 

Referring back to this country, Thomas Edison and Stephen 
D. Field began experimenting about the year 1880. Edison was 
principally interested in the development of the incandescent and 
arc lamps at this time and aside from building a short road at 
his laboratory at Menlo Park and taking out a few patents, he did 
little in this line. Field did considerable pioneer work, having 
made plans in 1879 for a railway to be supplied with power by 
means of a conductor enclosed in a conduit and using the rails 
as a return circuit. In 1880-81 he constructed and put into 
operation an experimental electrical locomotive at Stockbridge, 
Mass. Patents were applied for by Field, Siemens, and Edison 
within 3 months of each other early in 1880. Since Field had 
filed a caveat, however, the year before, his papers were given 
priority. Field's plans, however, remained on paper until the 
latter part of the year 1880 which was a year later than the 
installation of the Berlin road. 

Little more was accomplished in the United States until 1883, 



HISTORY OF ELECTRIC TRACTION 7 

when the interests of Edison and Field were united and the 
Electric Railway Company of the United States was organized. 
This company exhibited an electric locomotive at the Chicago 
Railway Exposition in 1883, which operated on a track about 
J:3 mile in length in the gallery of the exposition building. 
The motor operated a central driving shaft by means of bevel 
gears, this shaft being belted to one of the axles. The speed was 
varied by the use of resistances. Reverse motion was accom- 
plished by throwing into service an extra set of brushes by means 
of a lever, only one set of brushes, of course, being upon the com- 
mutator at any one time. 

Charles J. Van Depoele, a Belgian sculptor, who was destined 
to play an important part in the later development of electric 
traction, entered the field in 1882-83 when he operated a line in 
connection with the industrial Exposition at Chicago. After 
installing equipments at the New Orleans Exhibition and at 
Montgomery, Ala., and putting roads in operation at Windsor, 
Ont., Detroit, Mich., Appleton, Wis., and South Bend, Ind., the 
company which Van Depoele had formed was absorbed in 1888 
by the Thomson-Houston Co., which had recentlj^ been organ- 
ized. The name of Leo Daft is one that cannot be neglected 
in the development of this period, for after considerable work 
with stationar}^ motors in 1883 he constructed a locomotive 
capable of hauling a full-sized car. The control in this car was 
brought about by varying the resistance of the motor field for 
which purpose some of the coils were wound with iron wire in 
place of copper. The company organized by Daft at Green- 
ville, N. J., installed roads at Coney Island, N. Y., and the 
Mechanic's Fair in Boston, and in 1885 equipped the Baltimore 
Union Passenger Ry. Co. with electric locomotives. During 
this year electric traction was applied by this company to the 
Ninth Avenue lines in New York, but after a few experimental 
runs of the locomotive termed the '^ Benjamin Franklin" the 
experiment was abandoned. 

In 1884 Bentley and Knight installed a system in Cleveland, 
Ohio, which was probably the first to come into active competi- 
tion with a horse car line. Two miles of track were operated 
with underground conductor in wooden slotted conduit. ]\Iotors 
w^ere connected with car axles through the agency of wire cables. 

The railroad installed in Kansas City, Mo., in 1884, by J. C. 
Henry, was noteworthy for its departure from other designs and 



8 • ELECTRIC RAILWAY ENGINEERING 

its adoption of features which have since become standard prac- 
tice in electric railroading. Henry claims to have introduced the 
use of the overhead trolley. Whether this be true or not, the 
word 'Hrolley" was first coined by the employees upon this road 
as a contraction for 'Hroller, " the word first applied to the four- 
wheeled carriage which was used on the overhead wire as a 
current collector and connected with the car by means of a flexible 
cable. The use of the trolley rope for replacing the trolley was 
of much more significance than it would at first appear because 
of the fact that it was formerly customary to hire a boy to ride on 
top of the car to keep the trolley on the wire. The present sys- 
tem of span construction and feeder installation was first de- 
veloped by Henry on this road. His overhead conductors con- 
sisted of two No. 1 B. & S. bare copper wires spliced every 60 ft., 
for this was the greatest single length procurable at this time. 
The rails used were those which had been installed 12 years before 
for horse car service and weighed but 12 lb. per yard. They were 
at first bonded by driving horse-shoe nails between the fish plates 
and the rails. The motor was a 5 hp. Van Depoele type con- 
nected with the axles by means of a clutch and a 5-speed 
differential gearing. The generator was a series arc machine of 
10 hp. developing a voltage up to 1000 volts. Although Henry 
was able to mount 7 per cent, grades without difficulty, the 
Cleveland road was the only other practical road operating in 
America at that time and it was extremely difficult to gain the 
confidence of the public. 

Of the roads that were installed during the next few years, 
the one which gave the greatest impetus to electric traction and 
the one often quoted as the first electric road in the United States 
was that in Richmond, Va., equipped in the year 1888 by Frank 
J. Sprague. At this time Mr. Sprague was already prominent 
in the railway field, although much of his time had been given 
to the development of the stationary motor. In a paper before 
the Society of Arts of Boston in 1885 he had advocated the 
equipment of the New York Elevated Railway with motors 
carried upon the trucks of the regular cars. In 1886 a series of 
tests were carried on upon the tracks of the 34th Street branch 
of this road. These experiments, like many previous ones, how- 
ever, were finally suspended because of the impossibility of 
interesting the railway management sufficiently to launch out 
upon a commercial installation. 



HISTORY OF ELECTRIC TRACTION 9 

The motor design and suspension used by Sprague in these 
tests were the forerunners of present construction and therefore 
worthy of a brief description. The motor frame contained bear- 
ings mounted upon the car axle, thus permitting the former to 
swing sHghtly about the axle as a center, keeping the gear and pin- 
ion always in mesh on rough track. The other side of the motor 
frame was hung from the truck frame by means of springs. 
Single reduction gearing was used. Two motors were used on 
each truck but they were open to the weather. The first designs 
were shunt wound, but later types made use of a series compen- 
sating winding. Control was obtained by resistance in both 
armature and field circuits. The motors were used for return- 
ing energy to the line as well as for braking. 

Before considering further the rather important installation 
at Richmond, it is well to take a census of electric traction 
development early in 1887. In Europe at this time there were 
but 9 installations including but 20 miles of track, taking into 
consideration every type of electric traction including that in 
mines. In the United States there were 10 such installations 
involving 40 miles of track and 50 motor cars. Public prejudice 
had not been overcome and no system of any size had been 
operated commercially. 

The Sprague Electric Railway and Motor Company con- 
tracted for installations at St. Joseph, Mo., and Richmond, Va., 
during the year 1887, the latter contract covering a complete 
new road including generating station, overhead lines, and the 
equipment of 40 motor cars with two 73-^ hp. motors each. It 
was placed in operation in February, 1888, and many were the 
new experiences and amusing anecdotes connected with this 
installation. The distribution system consisted of an overhead 
conductor mounted over the center of the track with a second 
parallel conductor on the pole line supplied with feeders from 
the power station and extending to various distributing points. 
The power station was equipped with six 40 kw. 500 volt Edison 
generators driven by three 125 hp. engines. Upon each axle 
of the car was mounted an exposed motor in the manner pre- 
viously described. The single reduction gearing employed at 
first was later replaced by the double reduction type. The 
speed control was effected by two separate switches, one chang- 
ing the field connections from series to parallel and the other 
making similar changes in the armature circuit. The cars 



10 ELECTRIC RAILWAY ENGINEERING 

could be operated in either direction from either end and the 
entire weight of the car was available for traction. Motors 
were operated in both directions, at first with laminated brushes 
fixed at an angle and later with radial solid metallic brushes. 
The success of this road at Richmond, in the face of many re- 
verses and new engineering problems which had to be overcome, 
was probably largely due to the fact that Mr. Sprague was the 
first man with a competent education to enter the field. With 
this technical training together with his familiarity with the fail- 
ures of other experiments and the development of the stationary 
motor with which he was closely allied, he was able to solve the 
many difficult problems which arose and place this road on a 
practical operating basis. 

From this date electric traction became firmly seated and its 
future development was rapid, the natural tendency being to- 
ward heavier equipment. After investigation of the Richmond 
system the West End Railway of Boston soon adopted electric 
traction. In 1890 the South London road was equipped with 
electric locomotives and 3 years later the Liverpool overhead 
electric railway was put in operation. Third rail trains of four 
motor cars, equipped with hand control, hauling three trail cars, 
were used at the Chicago World's Fair in 1893 and in 1896 the 
Nantasket branch of the New York and New Haven Railway 
was electrified. September of the same year saw the Lake 
Street Elevated of Chicago begin electrical operation and 2 
months later electric service was begun on the Brooklyn Bridge. 

Since it is impossible further to list the new electric roads 
coming into existence the following table will be of value in point- 
ing out the remarkable growth of the electric railway in the 
United States. 

The most important changes in motor design that came with 
this progressive movement of the electric railway were the en- 
closing of the frame to protect the motor from the weather, the 
replacing of cast iron by steel, the change from two to four poles, 
the use of form wound coils and carbon brushes and the return to 
the old single gear reduction between motor and axle. The 
control system of 1892 made use of the combined resistance and 
series parallel connection, which is recognized as good practice 
to-day, while the introduction of the blow out magnet was a long 
step forward in controller design. 

The more recent developments in electric traction comprise 



HISTORY OF ELECTRIC TRACTION 



11 



the use of alternating current for transmission to substations, 
the multiple unit control of the various cars of a train from a 

Table 1. — Growth of Electric Traction in United States 



Year 



No. electric roads 



Miles track 



1889 


50 


100 


1890 


200 


1,200 


1891 


275 


2,250 


1894 


606 


7,470 


1895 (July) 


880 


10,863 


1902 


739 


22,000 


1907 


904 


34,000 


1912 


975 


40,800 



Note. — The decrease in the number of companies from 1895 to 1902 is 
probably due to the large amount of consolidation going on during this 
period. 

single master controller, field control of motors, the use of alternat- 
ing current and commutating pole direct current motors on the 
car, the electrification of steam roads with the more power- 
ful electric locomotives, regenerative braking and the use of 
high voltage direct current systems. These problems are of 
such a broad nature and so important in the study of modern 
practice that they will be taken up more in detail elsewhere. 
Suffice it to say, by way of historical comment, that the rapid 
introduction of interurban railways beginning about the year 
1894, together with the advances made in transformer design by 
Stanley, in polyphase transmission by Ferraris and Tesla and in 
the synchronous converter by Bradley and others, brought 
about the first of the above-mentioned changes, i.e., the use 
of alternating current for transmission purposes. Probably 
the first proposal to use such a system with substations was the 
one made by B. J. Arnold in 1896 for an interurban road to run 
out of Chicago. Although this particular line was not built, a 
similar system was installed about 2 years later. The multiple 
unit system was developed by F. J. Sprague who proposed its 
application to the New York Elevated Railway in 1896. After 
several vain endeavors to secure its adoption it was finally in- 
stalled the following year by the South Side Elevated Railroad 
of Chicago and is now in common use on elevated systems and 
is used to some extent in interurban traction. 



12 ELECTRIC RAILWAY ENGINEERING 

Summarizing briefly, the most prominent names in the develop- 
ment of the electric railway are found to be those of Faraday, 
Davenport, Farmer, Hall, Pacinotti, Siemens, Green, Field, Van 
Depoele, Daft, Bentley, Knight, Henry, and Sprague. While 
gradual developments have been going on more or less irregularly 
since 1835, the practical electric railroad, operating upon a com- 
mercial scale, dates back to about the year 1888. Vast strides 
have taken place since that date, however, until at the present 
time electric traction is the recognized transportation system in 
practically all cities and towns. It has tied together the larger 
cities with facilities for rapid passenger transit and for the trans- 
portation of both express and freight. It has opened up the city 
markets for the farmer of the small town, and the country sub- 
urbs for the residences of the city business man. It has com- 
peted successfully with the steam roads on interurban lines; it 
has found a foothold in the city terminals of the former, and is at 
present being seriously considered and in some particular cases 
has been adopted and successfully tried out for trunk line service. 
Rightly has it been said that its growth is without a parallel in 
the history of American invention and industrial progress. 



CHAPTER II 
TRAFFIC STUDIES (PREDETERMINED) 

One of the first considerations in connection with the planning 
of a new railroad or of an extension to an old system, whether 
it be within the limits of a city or an interurban line, is the study 
of probable traffic. Upon such a study is based the predeter- 
mination of gross income, train schedules, and power station 
demand. The importance, therefore, of an accurate and de- 
tailed study of all the factors which may affect the traffic upon a 
given road need not be emphasized further. 

Population. — A study of the railway census will disclose the 
fact that there is a fairly dependable relation between passenger 
traffic and population for both urban and interurban railroads. 
In the latter case, of course, the population under consideration 
must be that of the two terminal cities and, in most cases, a 
portion of the intermediate population which may be considered 
as tributary to the line. The determination of this tributary 
population is rather difficult, being largely dependent for its 
accuracy upon the experience and judgment of the engineer. In 
general, however, it is usually taken as the population of a 
strip of territory from IJ-^ to 2 miles in width on either side 
of the proposed railroad and parallel thereto. The population 
of such a strip may be determined by actual canvass or it may 
be assumed that the township or county through which the 
road extends is evenly populated throughout the rural districts. 
If this be true, the tributary population may be found from the 
following proportion: 

Tributary population _ Area strip 
Township population Area township 

The township population may be obtained from the census 
reports and the required areas scaled from a map of the territory 
in question. 

While it will be found advisable to make an analysis of the 
relation between population and passenger traffic per year, 
mileage of track economically operated, gross income, etc., for 

13 



14 ELECTRIC RAILWAY ENGINEERING 

the entire country, a table or series of curves covering such data 
obtained from the particular locality in which the proposed road 
is to be operated will be found of more value. The nearer the 
conditions of installation and operation of these roads approach 
those of the proposed road, the more dependable will be the 
results based thereon. 

A table giving data of value in predetermining the traffic and 
gross income for a proposed road is given herewith. 

Whereas such a table offers more opportunity for the correct 
comparison of traffic, etc., for an urban road or for extensions 
to such a system than for the predetermination of interurban 
traffic, yet the methods outlined may be used to advantage in 
interurban developments providing they are applied with con- 
servative judgment based upon successful interurban experience. 
As an example of such adaptation of data to interurban practice 
it should be noted that a different proportion of terminal popula- 
tion will be tributary to the traffic of the proposed road in each 
case under consideration. In the case of the road being the 
first to enter a relatively small terminal city, a large portion of 
the population of the city will avail itself of the road, but if the 
road is the fifth or sixth to enter such a city as Indianapolis or 
Chicago, a relatively small portion of the population of the termi- 
nal city can be counted upon for passenger traffic. It follows 
directly from this, therefore, that with a large terminal city 
the earnings of the road per capita of terminal population will 
be small and the earnings of a successful road per mile of track 
will be relatively large and vice versa. 

Growth in Population. — It is necessary, however, to know 
more than the present terminal and tributary population. The 
growth of both for several years to come must be predicted. In 
order to do this intelligently it is necessary to know the growth 
in the past not only, but to study the causes of any eccentricities 
in the growth curve. It is only after such a detailed study that 
the population curve may be accurately extended to determine 
the population to be expected 40 or 50 years hence. 

Bion J. Arnold, consulting engineer of Chicago, in his "Re- 
port on the Chicago Transportation Problem," points out very 
clearly the fallacy of predicting the population for any consider- 
able term of years by any rate of growth which has existed in the 
past, if the law of ''yearly decrease in the rate of increase " be 
neglected. If, by way of illustration, we refer to the curve of 



TRAFFIC STUDIES 



15 









O 






















CO 






2 


"^ 




00 


CO 


CO 


,_ 


■1 


CO 


CO t^ 00 OO CO t> 


o 




00 


CO 


Tt^ 


r- 




00 


lO <M CO O 00 lO ^ 
C^_ Oi O O CO (N '^ 


■—I 


o 




o 


lO 


CO 


1> 


00 


S3 

2 


H 


a 
.2 

1 


o 


o 


o 


o 


o 


1-t O O 1-H O i-H O 


13 


CO 


















00 lO 


*3 


CI 


1:^ 


i> 


CO 


y- 




lO 


00 CO CO 00 Oi 


CD 


s 


O^ 


CO 


Tt^ 


T— 


H 




00 CO (M CO l> 00 


::3 


o 


CO 


CO 


l> 


o 


00 CO o i> Tj^ i> Tt< 


S 


^ 




o 


O 


o 


o 


- 




T— 1 1— 1 O tH O T— 1 O 


oJ 






'^ 


00 














CO 1-H Oi I> 


'S. 


"^ 




c^ 


CO 


lO 


00 


iO 


(M CO Tti cq 00 CO -rhi 


g 


o 


G 


(M 


CO 


CO 


CO 


CO 


,-1 Oi IO Oi Oi rH rH 










H 






I— ( 


IQ 


o CO i> 1-H ^ 
1— 1 


-^ 


05 


















>0 (N 


fl 


s 


Ah 


-* 


(M 


iO 


00 


Oi 


CO O Tt^ (M 00 IO 1> 


i 




CO 


CO 


CO 


CO 


d 


rH lO lO lO (N CO .-H 


o3 


r'" 




I— 1 




< 










CO 


IO IO CO (M rH 


P-( 


H 






















1-H 1-H 




a 


CO 


Tt 




Oi 


(M 


c^ 


I> 00 lO CO Oi CQ CO 


^ 


m 


Oi 


O 


00 


o 


CO 


CO 1-H CO O O Oi t> 




1> 


1> 


Tt 




Oi 


CO 


(N Oi Oi 1-H 1-H Tt^ CO 


























00 


I> 


c^ 


(M 


»o 


00 1> C^ rH 1-H 00 00 


e 


■^ a2« 


Oi 


CT 




Tt 




Tj^ 


CO 


CO O IO O 00 00 o 




a 


00 


(M 


T- 








■^ 




T-H TJH C^ 1-H Tji (M 






















cf rn" 




^ fl 


T— 1 


Cv 




Oi 


(M 


00 


O Oi CO IO rH CO rt^ 




c3 O 


1> 


C^ 




00 


O 


CO 


O IO CO Oi O CO CO 




11 


lO. 


cr. 




T^ 


Oi 


Tf 




IO C^ O (N IO t- C<l 


























CO" 


T— 




c^ 




Cv 




<> 




c<r ^"^ ^'^ oi*^ oo'' c<f ^ 




« a 


T— 1 


XT. 




Tt- 




Tt 




oc 




1-H Oi TtH IO 1-H CO CO 




H g 


00 


(^ 




T— 








o: 




T-H cq (M rH O 




a 




















ccT i-h"^ 




(n M 


00 


Oi 


~ 




O 


CO 


CO (M CO O CO IO t^ 






to 


C£ 




cr. 




lO 


cc 




!>. 1-H rH 00 O Oi 1-H 




05 


I> 




a- 




c 




rh 




1-H 00 rH 1-H CO O rH 






1> 


cc 




"^ 




CC 




OC 
cc 




1-H 1> IO O 00 rH O 
(M CO 1-H tH rH ,-H to 




m 


rH 


<M 




o- 




1> 


Oi 


rH CO (M IO CO (M Oi 




M 


05 


Tt- 




c*: 




GO 


00 


Oi CO IO t^ CO t^ 1> 




"cS M 


CO 


1> 




^ 




N 




CO 


'^^ '^.^ ^^ ^^ ^^ '^ ^ 




Is 


oT 


Tt- 




N 


"^ 


O^ 


uf 


rn" 1-h" rH" lo" rn" 1-h" o" 




h| 


92 


\r. 




(N 




o- 




cc 




rH (M (M O (N CO (M 




Oi 


cc 




o- 




IC 




cc 




O O (M O lO O J> 




ft 


rH 


§ 












cc 




t^." co'^ C^" OO" Oi" 1-h" tC 

1-H tH rH rH 






O C3 




1 




^ 

^ 
^ 

'S 




1 




c!. 

03 

H 
















If 




:3 






W 




o3 
1 






03 t>, 1-1 










"o3 OJ 








p:? 




03 


















1 

■73 




+3 

1 




'o 

ft 

o3 




1— 1 

1 




of Indi 
[cago R 
3 an Rai 
Railwa 
ay Co. , 
i,v Co 






o 
O 


13 
i ° 

a 


C 


Pi 

o 

m 
'^ 
'ft 

c3 


c 
> 


O 
1— ( 

■g-c 

.1.1 


t— 1 


c 

c 

J 


O 

c 
« c 

■e § 


lion Traction Co. 
rora, Elgin & Chi 
ckford & Interurl 
Iwaukee Electric 
istern Ohio Railw 
io Electric Railwj 






1 


f§& 


O 


o 


Ph 


Q 


h^ 


H 


^ 


£ 


•^ 


( — 


^rtS^ 


O 


I 



16 



ELECTRIC RAILWAY ENGINEERING 



Fig. 1 which represents the population of the city of Phila- 
delphia during a long term of years, we shall see at once that 
had the future population of that city been predicted in 1860 from 
the rate of increase during the previous decade, the result 
would have been far from the fact. As a matter of fact, the rate 
of increase in population of Philadelphia dropped in 5 years 
from 33 per cent, per annum to 9.7 per cent, and, in another 



2,100,000 

1,950,000 

1,800,000 

1,650,000 

1,500,000 

1,350,000 

1,200,000 

1,050,000 

900,000 

750,000 

600,000 

450,000 

300,000 

150,000 



1 
































































POPULATION 

OF CITY OF 

PHILADELPHIA 

1800-1900 




























































1 


















<# 


/m 
















4 


y/ 


{ 














i 




Z 
















41/ 
















</ 


-■/ 














^ 






* 














^ 


y 


/ 
/ 












.=^ 


"?S' 


3 


f" 


w 











Fig. 1. 

5 years, to 2.9 per cent. Although this marked change in the 
rate of increase of population is exceptional in the case of Phila- 
delphia, Arnold found that in the cases of the eight largest cities 
of the world which he studied the average rate of increase in 
population is gradually decreasing. It is obvious, therefore, 
that even if the average rate of increase in population over a 
long term of years were applied to the future growth of a city, 



TRAFFIC STUDIES 



17 



the results would still be too high. As an illustration, the 
average rate of increase in Chicago from 1837 to 1902 was 8.6 
per cent, per annum, from 1892 to 1902 it was 4.9 per cent., and 
during the j^ear 1902 it was 7.7 per cent. Beginning with the 
3'ear 1900 and compounding the population at 5 per cent., the 
resulting value for the 3^ear 1952 would be 18,500,000, while an 8 
per cent, increase, compounded, would give this city a population 



4,650,000 
4,500,000 

4,350,000 
4,300,000 
4,050,000 
3,900,000 
3,750,000 
8,(300,000 
3,450,000 
3,300,000 
3,150,000 
3,000,000 
2,850,000 
2,700,000 





















































H 








POPULATION OF 
CITY OF 




L 




LONDON 
1861-1901 




' 








! 








.^y 






















H 
















1 


// 


















1 


































1^/ 












1 




4r 


i 


















Wi. 


7^ 
































, / 















Fig. 2. 

of 26,500,000 in oilty 35 ^^ears. With the use of the more correct 
method, however, which takes into consideration the fact that 
the rate of increase is continually on the decline, the population is 
compounded with a constantly decreasing percentage. Such a 
method applied to the city of Chicago and beginning with the 1902 
rate of 7 per cent, results in a predicted population of 13,250,000 
for the year 1952. It is probable that this will mark the upper 

2 



18 



ELECTRIC RAILWAY ENGINEERING 



limit of the actual population curve, while the minimum limit 
of the area within which the population will fall in the next 50 
years will be determined by a similar method of reasoning be- 
ginning with an increase rate of 3 per cent, which represents 
the average growth of the large European cities. The result 
of the latter calculation gives Chicago a population of 5,250,000 
in 1952. 

2,700,000 




Fig. 3. 



Reference to Figs. 2, 3, and 4 will give an idea of the changing 
rates of increase in population of the cities of London, Paris, and 
New York respectively. Several decades will be noted in these 
curves during which these rates have been abnormal ; these rates, 
if used as a basis for the predetermination of future population, 
would lead to very erroneous results. 



TRAFFIC STUDIES 



19 



Riding Habit. — The proper determination of the ''riding 
habit" for a given community or the number of passengers per 
capita of population per annum is important if the traffic of a 
proposed road is to be correctly predicted. This is always a 
local problem, dependent upon the geographical and industrial 
features of the country or city under consideration, as well as 
upon the customs of the people, the existing or possible forms of 



2,100,000 
1,950,000 
1,800,000 
1,650,000 
1,500,000 
1,350,000 
1,200,000 












































POPULATION 
OF CITY OF 

NEW YORK 
1800-1890 










































%M- 


















/ 
















i\ 


7 
















A 


/ 


5^0 




l,OoO,(XX) 
900,000 
































■A 


r 


^ 






750,000 
600,000 
.450,000 
300,000 
150,000 










^* 


4 


f 














n 


// 


t/ 
















^ 


/" 


i 














y 


j^.3 


, 












"^^ 


i^ 


'2.n 

















Fig. 4. 

recreation, etc. In the case of the interurban road little aid 
can be obtained from tabulated results upon other roads, for 
the possibility of comparison with a road where the conditions 
outlined above are the same is very small. For urban roads, 
however, reference may well be made to a curve (Fig. 5) plotted 
between ''passengers per capita per annum" and population 
throughout the country. This curve has been shown by one 



20 



ELECTRIC RAILWAY ENGINEERING 



author^ to rise from approximately 70 passengers per capita 
per annum in cities of 15,000 population to a constant value of 
240 in cities of 1,000,000 inhabitants and over, although Arnold's 
results in Chicago show an increase from 150 to 182 passengers 
per capita per annum from 1891 to 1901. 

Competition. — The question of competition with steam roads 
is a vital one with most interurban and suburban railroads, 
whereas most urban systems are practically monopolies. 



220 

200 

eslSO 

6 160 

u 
o 
PhMO 

M 

Il20 

a 

0) 

1 100 

P4 



60 



40 



90 







■ 






























— 


— 


— 


— 














































. — 


-- 


-^ 


























































u 
























































/' 


^ 




















































-- 








/ 




























































/ 






























































/ 






























































/ 
































































/ 
















RELATION OF ANNUAL PASSENGERS 
PER CAPITA TO POPULATION. 


















/ 


































/ 
































































































































/ 
































































/ 































































































































































































































































































































































































































































































































































































































































































































500,000 



1,000,000 



1,500,000 



Population 
Fig. 5. 



If the proposed road is to parallel a steam line, it is usually 
advisable to make a study of the traffic conditions on such an 
existing line, either from authentic records or by actual counting 
of passengers on all trains in the various seasons of the year. 
Such records must be applied with great caution, however, for 
it has been found that a well-equipped interurban line with fre- 
quent and' high speed service often takes away much local traffic 
from the parallel steam lines not only, but, in addition, creates a 
traffic of its own. In other words, if the public can make a trip 
at any time of the day desired, if the cars are clean, free from 
smoke and cinders, and comfortable, and if the time lost en route 

^ See "Electric Railways," Vol. II, by S. W. Ashe. 



TRAFFIC STUDIES 



21 



is a minimum, it has been found that many ride who would other- 
wise remain at home. It is difficult to obtain more than a very 
rough approximation, therefore, of future traffic from steam rail- 
road statistics. That preference is given to the electric road and 
that traffic is often greatly reduced on existing steam lines with 
the advent of the electric interurban line is clearly shown by the 
figures in the following table. 



T.^LE 111. 


—Traffic on Lake Shore and Michigan Southe 
Cleveland and Oberlin^ 


RN between 




1 

Westbound , Eastbound 


Total 


Average per 
month 


1895 

1902.. 


104,426 
46,328 


98,588 
45,433 


203,014 
91,761 


16,918 
7,647 



Gross Income. — After having studied all statistics and local 
conditions which may possibly have a bearing upon the future 
traffic of a proposed road and having approximated from such 
study, combined with the riding habit of the people, the total 
traffic that may be expected with its hourly, daily, and season 
wide fluctuations, it will be necessary to determine the gross in- 
come possible from such a road. This may be done either by 
applying the average fare paid per passenger to the above traffic 
figures, which total may be augmented in some cases by express, 
freight, and mail receipts; or a comparison may be made with 
other similar roads operating successfully in the same locality and 
under similar conditions. Such a comparison based upon units 
of gross income per capita of terminal or tributary population or 
per mile of track gives very satisfactory results, as will be seen 
from the follow^ing example. 

Electric railways from the beginning have handled more or 
less freight, mail and -express, but only within the last few years 
have the managements of electric railways begun to look on such 
traffic as an important source of revenue. Very few electric 
railways can afford the equipment necessary to carry on inter- 
change traffic with steam roads. By reason of the quick service 
they offer, electric railways have found favor with shippers of 
package freight destined for local points. They often cooperate 
with steam roads, serving as gatherers and distributors of carload 

^ See "American Electric Railway Practice," by Herrick and Boynton 
p. 4. 



22 ELECTRIC RAILWAY ENGINEERING 

lot freight, gathering carloads of grain, fruit, sand, stone, etc., 
along their lines and turning them over to steam roads with 
which they make physical connection, and receiving from the 
steam roads carloads of coal, oil, and similar freight for distribu- 
tion. The revenues from freight traffic of the various electric 
railways differ greatly, varying with the different roads from 1 
per cent, to 50 per cent, of the gross earnings. According to the 
United States Railway Census for 1912 the number of electric 
cars used for hauling freight, express, mail and baggage increased 
from 11 14 in 1902 to 7794 in 1912 and the revenues from $1,871,- 
849 to $14,577,203. Only after a very careful study of local 
conditions can an estimate be made of the probable freight 
revenues of a proposed road. This estimate should be checked, 
when possible, by comparison with the actual revenues of other 
electric railways operating under similar conditions. 

In determining the gross income for a proposed 50 mile electric 
interurban line in Texas, connecting cities of 34,000 and 58,000 
inhabitants, comparison was made with two other roads operating 
under similar conditions with the following results. 

One of these roads, in the same state, connected cities of 15,000 
population each with 16 miles of track, returning a gross income 
in 1905 of $3.48 per capita of terminal population, while the 
second road, 81 miles in length, connecting cities of 26,000 and 
52,000 population, earned a gross income of $8.45 per capita. 
Taking the more conservative value of $3.48 from the former 
road as a basis, the minimum return from the new road should 
be approximately 92,000 X $3.48 or $321,000, representing an 
earning of $6420 per mile. This figure compares very favorably 
with the corresponding values of $8160 and $6540 per mile 
for the two roads previously referred to. 

In order to determine the net income it would be possible, of 
course, to approximate the operating expenses, fixed charges, 
etc., in detail, and subtract them from the gross income. A fair 
average ratio of net to gross income is often taken, however, as 
45 per cent. This figure applied to this particular road shows a 
net income of $144,500 annually and therefore a possible operating 
expense of $176,500. 

Number and Capacity of Cars. — The determination of the 
number and therefore the necessary carrying capacity of cars is 
sometimes arrived at as follows:^ 

1 See "Electric Railways," by S. W. Ashe, p. 16, Vol. II. 



TRAFFIC STUDIES 23 

A well conducted road may safely be assumed to earn 20 
cts. per car mile. The car mileage per year may therefore be 
roughly obtained by dividing the gross income by the factor (0.2). 
The number of car miles per hour is, of course, readily deduced 
from the above quotient by dividing by the hours of actual car 
operation per year. If, then, the average schedule speed is speci- 
fied by city ordinance or is decided upon by the railway officials, 
the number of cars may readily be determined from the equation 

-^ , . Car miles per hour 

JN umber oi cars = 



Schedule speed in miles per hour 

However, the above result can be more satisfactorily and correctly 
obtained in most cases from train schedules. The total traffic 
to be expected having been calculated as explained above, the 
headway or schedule speed of cars is usually readily decided upon 
with a view toward carrying this amount of traffic or in order to 
meet successfully the competition of parallel steam roads. The 
graphical train schedule sheet explained in detail in Chapter IV 
may then be plotted, whereupon the number of cars necessary to 
maintain the proposed schedule immediately becomes apparent. 

It would be possible, of course, to determine the seating 
capacity and size of cars to be purchased for a given road from 
the theoretical calculation of the probable number of passengers 
per trip at various times of day and at various seasons of year, 
but such calculations seldom, if ever, become controlling features 
in the purchase of cars for a given road. For interurban roads 
the size and capacity of cars have been very well standardized 
by custom, the increased traffic at times being handled by changes 
in schedule or by the operation of two or more cars together in a 
train on the same schedule. As will be seen in the following 
chapter, how^ever, cars are seldom operated at their exact seating 
capacity, and in spite of the fact that standing in cars on inter- 
urban trips becomes most tedious and oppressive and granting 
the conclusions discussed more at length in the following pages 
that a considerable percentage of passengers stand in cars by 
preference, yet it is a regrettable fact that the size and headway 
of cars on many roads, especially in cases of urban traffic, are 
determined with but little consideration of the ratio of seating 
capacity to passenger traffic. 

On interurban railways, mail, express, and milk are often 
carried in the baggage compartments of the regular passenger 



24 ELECTRIC RAILWAY ENGINEERING 

cars. Freight is carried in motor cars designed for the purpose 
and in standard freight cars hauled either by locomotives or 
motor cars. No general rule can be given for the calculation of 
the number of freight cars necessary to handle the freight traffic 
of a proposed road, but a careful study of the country traversed 
by the road will furnish data valuable for estimating purposes. 



CHAPTER III 
TRAFFIC STUDIES (EXISTING) 

The necessity of making a careful study of existing traffic upon 
urban, interurban, and even steam railroads for the purpose of 
comparison with the conditions of a proposed line and in order 
intelligently to predetermine the probable income from, and 
therefore the advisability of financing and building a new line, 
has already been set forth. Further than this, those responsible 
for the successful operation of present and future lines must 
continually study the condition and tendencies of traffic. Quot- 
ing from an editorial in the Electric Railway Journal upon 
this point: ''The managers of city railway systems which do not 
embrace more than a half-dozen routes usually feel that they 
know every detail of the traffic distribution so well that it is 
unnecessary to go to the trouble of preparing graphic records. 
The correctness of this point of view, how^ever, is not proved by 
the experience of those who have had occasion to prepare traffic 
curves, even for cities of less than 40,000 population, as they 
have found that such curves will betray the riding peculiarities of 
the public much more clearly than a mere tabulation. From such 
a record, for example, it is easy to observe whether the passengers 
take kindly to short trip cars or neglect them in favor of through 
cars even when they do not ride to the end of the line." 

"Traffic curves, furthermore, are not only of value to the com- 
pany in making up its schedule, but are also an aid in its relations 
to the public. When a complaint is made about the service on a 
certain line, it is surely convenient to be able to prove graphically 
that in the course of the day's operation the number of seats 
furnished far exceed the passengers and that the schedules 
adopted are based strictly upon the amount of traffic which the 
line brings." 

While reports of traffic investigations have been made public 
from time to time, especially as the results of studies by consulting 
engineers in connection with proposed improvements in the rail- 
way system for the purpose of reducing congestion of traffic by 

25 



26 ELECTRIC RAILWAY ENGINEERING 

means of subways, elevated lines, rerouting of cars, introduction 
of prepayment cars, etc., yet little- has been said regarding the 
best methods of making such detailed studies with any degree of 
accuracy. In fact the difficulty in obtaining accurate and de- 
pendable results has often been given as an excuse for not under- 
taking such a study. It is also true that where conditions of 
traffic are most variable, and these difficulties, therefore, most 
pronounced, the need of such an investigation is usually greatest 
and, when undertaken, results in the greatest possible improve- 
ment in service. 

It has been found where these traffic studies have been success- 
fully made that it is necessary to obtain data entirely independent 
of the daily returns of employees and that these data should be 
obtained by a crew of technically trained observers who under- 
stand the significance of every reading taken. The . average 
car employee, no matter how loyal and conscientious, usually 
not understanding the use to be made of the data collected and 
the relative accuracy with which the various readings should be 
taken, has been found unsatisfactory for this work. 

It is usually advisable to subdivide the city roughly into dis- 
tricts such as business, manufacturing, residence, etc., and then 
to make a detailed study of the riding habits of the people and 
the loading of the cars on a single route or division at a time. 
It will at once be observed that the day may readily be divided 
into several periods of peak load, usually four in number. One 
city whose traffic conditions were investigated recently by the 
Wisconsin State Commission was found to have its four periods 
of peak load extending from 6.00 to 9.00 a. m., 11.00 a. m. to 2.00 
p. M., 5.00 to 8.00 P.M., and from 10.00 to 11.00 p.m., respectively.^ 
The last was, of course, the theatre period and was therefore 
limited to a small district of the city. 

In studying the problem further, it is usually found that the 
public at large has a very well-defined habit of travel which 
does not vary greatly from one end of the year to another. 
Pleasure seekers and shoppers, of course, are irregular in their 
movements, but the majority of passengers will soon be found 
to follow not only a definite route in their traveling, but certain 
classes may be depended upon to ride during certain periods of 
the day. The above-mentioned residence districts of the city 

1 Graduate Thesis, Purdue University, 1910, by R. W. Harris. 



TRAFFIC STUDIES 27 

and the passengers as well may, therefore, be still further sub- 
divided as follows: 

1. Business or professional. 

2. Clerks and shoppers. 

3. Laborers. 

With such classifications in mind, it is necessary that the 
inspectors ride over the route or division under investigation a 
number of times during all periods of the day and in all kinds of 
weather to note roughly the effects of time of day, weather, and 
all local conditions upon maximum traffic. Especial notice 
should be taken of the stops which are of most importance, i.e., 
those at which most passengers leave and board cars. 

After such preliminary study the number of inspectors neces- 
sary, the particular stops to be studied, data to be recorded, and 
the number of readings to be taken in the detailed investigation 
may be decided upon. These readings may be taken by in- 
spectors, provided with stop watches, located at the principal 
stopping points; or, if the number of cars is not too great, an 
inspector may be assigned to each car on the route. In general 
the observations to be made at the most important stops are as 
follows : 

1. Line (route). 

2. Period of day. 

3. Exact time. 

4. Direction of car. 

5. Number of car. 

6. Total number of people on car. 

7. Number of people standing in front vestibule. 

8. Number of people standing in rear vestibule. 

9. Duration of stop. 

10. Number of people getting off car. 
IL Number of people getting on car. 

12. Class of passengers. 

13. Conditions of vehicular traffic. 

14. Conditions of pedestrian traffic. 

With symbols to represent many of the above conditions upon 
data sheets carefully prepared in advance and with a little ex- 
perience on the part of the inspector, the above data have been 
found to be readily and accurately taken. In fact in the investi- 
gations above alluded to check observations, taken independently 
but at the same time and place, varied less than 5 per cent. This 



28 



ELECTRIC RAILWAY ENGINEERING 



is sufficiently accurate for the determinations desired. A con- 
venient curve resulting from such data is found in Fig. 6. 

The results of an extensive investigation carried on in this way 
in one of the large cities of the west are typified by the single 
example represented by Fig. 7, in which the shaded areas repre- 
sent the various districts served by the particular car line under 
consideration, while the ordinates of the upper curve represent 
the passengers on the car during the period of maximum traffic 
extending from 5.00 to 8.00 p. m. The abscissae of both curves 
represent the distance in miles on either side of the center of the 



5 
























































r 




























^ 
p 


\ 


























\ 


\ 




























^^ 


















































1 






















































n 


























. _. 



2 4 6 8 10 12 14 16 18 20 22 24 26 
No. of Passengers Leaving and Entering Car 

Fig. 6. — Duration of car stop per passenger. 

city, while the full lines and dotted lines of the upper curve 
represent out-going and in-coming cars, respectively. It will be 
readily seen that the traffic at this time of day is largely from the 
city outward, as would be expected. Another point of signifi- 
cance is the fact that out-going cars from G to A take on the 
greater portion of their passengers between G and E, which is the 
retail business district of the division, and deposit them prin- 
cipally between C and A, which is in the mixed residence district. 
These passengers may properly be classed, therefore, as ''clerks 
and shoppers." On the other hand, the cars running from G 
to K take on their passengers between G and H within the 
wholesale business and manufacturing districts and deposit 
them between I and K in the third-class residence district. This 
leads us to classify this traffic as ''laborers." In a similar 
manner it is possible to determine from curves resulting from 



TRAFFIC STUDIES 



29 



careful investigation the tendency and amount of traffic on each 
division at all times of day. 

In order to determine, however, whether or not sufficient cars 
of ample capacity are being supplied, the ''comfortable load" 
per car must be decided upon. During such investigations in 
several of the larger cities it has been found that a considerable 
number of the passengers on a car stand by preference. In Fig. 8, 
curves A and A' show the total and percentage increase respect- 
ively^ of passengers standing by preference as the number of 



























1 1 1 1 1 1 1 










































CAR DEMAND CURVES 










































































«o- 




















/ 




































• 70- 












i/ 


























1 








!«, 












> 


\y 


r 




















^ 




























^ 




















) 












n\ 










o 
















1 






s 








/ 






1 


Coinforta 


3le\ Load 


















/ 




i 




1 


\ 






/ 


y 
















\ 
















/ 


1 








1 






./ 


/ 


















\ 








1 








A 












1 




\, 


<, 




























Ph so- 








/ 




i 


■ 




! 




/ 




\ 


























so- 






/ 


1 








! 




1 


J 








X 


\ 


















\ 








/ 




1 








i-' 




1 
















^ 














\ 




10- 


J 


/ 




1- 


- - 


-jr" 




j 




I 
























r^ 


■^ 






V 




L 










[ 




1 




1 
























1 




^ 




^ 




^ ;iO 1 20 

i 1 ! 

' iliied !,• 2, 3 Class Res. 
A E C 6 L 


1 30 40 
1 Blocks 
! (10 Blocks =1 Mile 
Dis 


i 50 ; CO 

1 t-Out 

1 Uln 


■-- 





i 


3rd Class Res. DJs.> N^ 



Fig. 7. 
passengers on the car increases in a city of 25,000 population, 
while curves B and B' show curves of similar tendency for a 
city of 330,000 in the Middle West. Referring to curve B and 
with the knowledge that the cars operated in this city will seat 
42 passengers, it will be noted that when the car is fully loaded 
8 will, on the average, stand by preference. The comfortable 
load has therefore been taken as 50 passengers and the variation 
of the ''car demand" curves of Fig. 7 above and below the 
"comfortable load" line indicates at once the quality of service 
being rendered. 



30 



ELECTRIC RAILWAY ENGINEERING 



It cannot be reasonably expected by the public that sufficient 
cars shall be furnished to enable every one to have a seat at all 
times of day, for many of the peak loads come on so suddenly 
and often so unexpectedly that it would be impossible to have 



















■ 






~ 










... 


































































































































PASSENGERS STANDING BY PREFERENCE 


















































































































































































































































































B 










































































1 
























































^ 


^ 


^ 


^ 










I 
































































\ 




















































^ 


LX 


















\ 
















































^^ 






















) 












































^ 


^ 




























\ 






































X 


x- 
































\ 


































x- 


^ 




























_ 


_ 


A- 







s 


^ 


^ 


^ 




_ 


_ 


_ 






_ 






-^ 


^ 


^ 


^ 




__ 




~4 




^ 


_ 


_ 


_ 


£ 


_ 









- 


— 




— 




- 




— 


— 


=!? 


^ 




-^ 






^ 


s 


p 




^ 




= 




A 


— 


p 


- 


- 


— 


— 


— 


— 


— 




— 






























^ 


^ 
































































, — 


^ 


f^ 
































































<: 


^ 
































































•^ 


^ 


































































^ 


^ 




































































A 



































































7 35 
6 30 
5 25 
4 20 

8 15 
2 10 
1 5 



1-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-43 

Total Number of Passengers on Car 

Fig. 8. 

the necessary cars at the proper time and place if it were the 
policy of the company to accomodate the peak traffic with seats. 
Most progressive companies, however, endeavor to meet the just 
demands of the riding public and therefore should determine 
those demands from time to time by methods similar to those 
outlined above. 



CHAPTER IV 
TRAIN SCHEDULES 

Having studied in the two previous chapters the important 
elements underlying the determination of probable traffic on a 
new railway line or upon the extension of an old system, it be- 
comes necessary to establish the train schedule. As has been 
previously inferred, this is often a question of judgment to be 
exercised by the executive head of the road in view of the necessity 
of meeting competition. That is to say, the engineer who plans 
the details of the train schedule is instructed to arrange for 
hourly or half hourly interurban service, as the case may be, or 
the headway expressed in minutes or distance between cars in 
feet may be specified in the urban system. In both types of 
system the limiting schedule speed is usually stipulated, often 
by the municipalities involved. The interurban system is usu- 
ally limited to two or more different schedule speeds, the higher 
velocities being confined to operation over private right of way 
and the lower within city limits or upon particularly dangerous 
sections of track such as trestles, drawbridges, and temporary 
construction. 

Whereas the hours of train arrival and departure are usually 
placed in the hands of the public in the form of time tables, 
the most convenient and common form for the study of these 
data by railwa}^ engineers is the graphical chart. Many factors 
entering into the proper construction and successful operation of 
a road are at once apparent from such a chart or graphical train 
schedule. This train schedule is often plotted with time of day 
in hours and minutes as ordinates and distances expressed in miles 
as abscissae. It is convenient if the ordinates representing the 
hours be designated by heavy lines on the coordinate paper and 
if the hourly sections be subdivided into sixths or twelfths, rep- 
resenting 10 and 5 minute intervals respectively. Upon the 
distance scale it is customary to designate the distance between 
stations and the location of any points of especial engineering 
interest along the line such as branch lines, railway crossings, 

31 



32 



ELECTRIC RAILWAY ENGINEERING 



city and township limits, etc. With the scales of coordinates 
thus determined, a series of slanting lines. Fig. 9, may be drawn 
to represent the progress of the train from station to station. 
The slope of these lines is, of course, dependent upon speed, the 
co-tangent of the angle which they make with the horizontal 
representing the schedule speed of the train. A chart made up of 
such straight lines representing each train leaving the terminals 
of the line in either direction is sufficiently accurate for a rough 
preliminary study of traffic possibilities, power requirements, 





"11 "II 


























"T" 














■ ■ 




■ 








' ■ 1 1 




































~ 












jt ,' ' 


















































, 


tf 


«.30 












































^' 




It 




>» 






































, 






it 








» . 






























. 




i^-' 








jf 
































































^ 


. 






















-* 
































^ 




















































V. 










^ 


























-. 




















-V 




•^ 
















^ 














~ . 




















;< 
















pt' 
































































" . 








h 


■> 






, 


^ 


■ 1 










V 






^ 






























-, 


















' 


Y 












^ 
















^ 


^ 






^ 










^ 


















































^ 
















, 














>r' 




















:< 
















■>r 


































,'' 
















. ^ 




IT 




















^ 


, 




, 


^ 


' 






















1 
























:^ 


















' 


^ 












5 
















^ 


^ 






^ 










. 






















>, 








































•A 












■" 


• r 




















;< 
















>; 














^ " 




^« 
















-' 
















-■' 




rr 


















~ 


V 


^ 




_. 


^ 


■ 










^ 






,< 








^ ^ 


1 


vA. 


















>^ 


- 
















- 


r" 


'^ 


J.._ 




-| 


- J- 


7.30 












^ 


' 






1^ 














"= 


^ 




,* 












■ 


~« 




















JL 














^ 




















:< 
















■>r 


1 
































, ' 
















.-- 




"■ 




















^ 


, 






^ 












^ 






^ 






























> 


' 
















' 


^ ■ 
















7.00 


. 












•' 






V 




















^ 


















^' 
















>v 




^ 






























^ 




































- V, 












__, 


























^ 
















"^ 




























^ 


































! ■ ■ jL 














^ 


' 


















■^. 


















jr 










^ 


■' 
























■> 
















ir 




















































11 


, 




























































































*> 










^p 




















































• ' 
















































"[ 


6.00 


















































> 










































































































_ 

|i;24 52 
3l7 3V'l- Rd. 
City Limit 

R^ vl R. 


89 




Ge 


8 
uoa 






18 


1 


V 


21 

ebs 

Le 


l2 , 
ter 

24 
ague 


4 
Ci 


2 
Die 


.5 

lliDtt 


a 


ii 


9 


L. 


36 4 

Mar,, 

T.'l 


ue G. 

38.9 

.Co.Ry 


42 


C.t 


G 

4 

L 


I-IIrii 



SO 

Galvestoa 



Fig. 9. — Intemrban train schedule (preliminary). 



and substation locations, but before exact time tables can be 
adjusted and meeting points determined, a very much more ac- 
curate and detailed graphical train schedule must be drawn. 
Such a schedule, involving three different schedule speeds over the 
various sections of road as well as the representation of the time 
elapsed in making station stops, is shown in Fig. 10, which is the 
proposed train schedule for a 50.6 mile interurban fine now 
connecting the cities of Galveston and Houston, Texas, within 
whose Hmits the schedule speed was to be confined to 10 m.p.h. It 



TRAIN SCHEDULES 



33 



should be noted that speeds of 30 m.p.h. and 55 m.p.h. are 
adopted for portions of the private right of way, while 1 minute 
has been allowed for the average station stop. Such a graphical 
schedule enables one to predetermine not only the number of 
cars necessary to maintain a given schedule and the position of 
those cars at any moment, but it locates the meeting points, 
which are designated by the crossing of the schedule lines, and, 
when used in conjunction with the power curves of the various 
cars, it aids in locating substations and in determining the average 




20 Miles 30 

Fig. 10. — Interurban train schedule (finalj 



42.3 
G.C.i-i 
38.9 
T.T.Co.Ey. City 1 

Draw of Bridge 
■iO 50 

GalvestOii 



and maximum loads on substations and power station. Com- 
paring Figs. 9 and 10 it will be noticed that while the former has 
the same through schedule speed as the latter and while all con- 
siderations based upon the headway and the time of leaving and 
arrival at terminal cities, taken from Fig. 9, are quite as accurate 
as those taken from the more detailed chart. Fig. 10, yet it 
is clear that nothing of value can be learned from the former 
regarding the meeting points nor the positions of trains at any 
moment. 

3 



34 ELECTRIC RAILWAY ENGINEERING 

A convenient way in which to study the possible changes in 
schedule upon a given line is to stick pins into the draughting 
board at points corresponding with the various stations and 
the hours of leaving and arrival at terminals or way stations. 
A number of strings stretched over these pins indicate imme- 
diately the relative speeds and meeting points required to make 
the desired schedule. The ease with which the strings may be 
changed from 1 minute of time to another, or from station to 
station, immediately commends the method to the busy traffic 
supervisor. 

Although local conditions will prevent any extensive com- 
parison of train schedules of different roads or even the schedules 
of the same road at different seasons of year, yet it is believed 
that the principal factors to be borne in mind in plotting sched- 
ules can best be outlined by a more detailed study of the par- 
ticular schedule of Fig. 10. 

This schedule is one proposed for maximum summer traffic. 
It will be noted that the first trains in the morning leave both 
terminals simultaneously at 6.00 a. m., and make the run in 
1 hour and 45 minutes, requiring a through schedule speed of 

— Vtts = 29 m.p.h. Further reference to the schedule will 

lUo 

show that of this total time only 43 minutes are spent on the 

private right of way where the maximum speed of 55 m.p.h. is 

possible. While all trains stop at all stations within the city 

limits, there are a number of flag stops between these limits 

which tend to make the operating schedule irregular but which 

for convenience in plotting can be represented fairly accurately 

by allowing three flag stops for each train between the Southern 

Pacific Railway crossing and that of the T. C. T. Co., at which 

crossings all trains are required to stop. 

The corresponding points of meeting as graphically deter- 
mined fall sufficiently close together to be provided for by the 6 
sidings shown at B, C, D, E, F, G, which are approximately 
1 mile in length. These could be materially shortened by vary- 
ing the running time slightly. The meeting places within the 
city limits are so numerous that a double track extending from 
6 to 7 miles out of the city terminals would seem advisable from 
this preliminary study. 

The time table below, which was taken from the graphical 
schedule represented by Fig. 10, will be self-explanatory and a 



TRAIN SCHEDULES 



35 



comparison of the table and chart will illustrate the advantages 
of the graphical method, even if the time table were to be the only- 
result obtained therefrom. 

T.\BLE IV.— Time Table (Predetermined) 



Stations 



North 



South 



Houston.. . . 

Genoa 

Webster. . . . 
League City 
Dickinson. . 
LaMarque. . 
Galveston. . 



6.00 


6.30 


7.00 


7.30 


8.00 


7.45 


8.15 


8.45 


9.15 


6.39 


7.08 


7.39 


8.09 


8.38 


7.04 


7.35 


8.05 


8.34 


6.48 


7.18 


7.48 


8.18 


8.49 


6.55 


7.27 


7.56 


8.26 


6.52 


7.21 


7.52 


8.22 


8.52 


6.52 


7.23 


7.52 


8.23 


6.56 


7.25 


7.57 


8.26 


8.56 


6.47 


7.19 


7.48 


8.18 


7.05 


7.36 


8.06 


8.35 


9.06 


6.38 


7.09 


7.38 


8.09 


7.45 


8.15 


8.45 


9.15 


9.45 


6.00 


6.30 


7.00 


7.30 



9.45 
9.05 
8.56 
8.52 
8.48 
8.39 
8.00 



The interurban road whose schedule was predetermined in 
accordance with the charts of Figs. 9 and 10 has now been in 
operation for several years, and its time table of first-class pas- 
senger cars is indicated in Table V. This is of interest in de- 
termining the accuracy with which such schedules can be pre- 
dicted for a proposed road. 

Table V. — Time Table (Operating) 



Stations 



North 



South 



Houston. . . . 

Genoa 

League City 
Dickinson. . . 
LaMarque . . 
Galveston. . . 



6.00 


7.00 


8.00 


7.40 


8.40 


6.35 


7.35 


8.35 


7.05 


8.05 


6.50 


7.50 


8.50 


6.50 


7.50 


6.54 


7.54 


8.54 


6.45 


7.45 


7.06 


8.06 


9.06 


6.33 


7.33 


7.40 


8.40 


9.40 


6.00 


7.00 



9.40 
9.05 
8.50 
8.45 
8.33 
8.00 



It has been previously stated that one of the advantages of the 
modern interurban system in competition with steam roads is 
its ability to transport the passenger to more nearly the exact 
point in a terminal city to which he wishes to go and often gives 
him transfer privileges upon the local railway system if necessary. 
When comparing, therefore, the graphical train schedule of the 
interurban line with that of the competing steam road, especially 
with regard to the relatively long time required by the former 
within the city limits, it is often advisable to add to the steam 
schedule the walking time from terminal station to a point repre- 
senting the average destination of the traveling public if such 
can be found. Such '^ walking schedule" lines added to the train 



36 ELECTRIC RAILWAY ENGINEERING 

schedule often bring out very striking facts in favor of the electric 
railway as a popular choice of means of transportation. 

The particular schedule taken for illustration is a relatively 
simple one. With the addition of limited and local service and 
possibly freight and mail trains, and, in some cases, the necessity 
of meeting the schedules of trunk or branch lines, the graphical 
chart often becomes rather complicated. The use of a large 
scale drawing, however, usually permits such a solution to be 
made with little difficulty. In fact such schedules have been very 
satisfactorily used with the varied types of service outlined above, 
but with the additional requirement that the train be made up 
of a varying number of cars controlled by the multiple unit system, 
the various cars being feeders to the trunk line from the branches 
en route and being joined together at the junction stations, thus 
forming the trains to enter the terminal city. The trains leaving 
the terminal city would operate in the reverse order, dropping car 
after - car to the various branches and having relatively few 
through cars from terminal to terminal. 

In steam railway electrification studies, graphic time tables are 
of considerable assistance in the analysis of operating conditions 
with existing steam motive power and in the determination of pos- 
sible savings in time, number of trains, and train schedules with 
electric motive power. Graphic time tables for days of average 
and maximum traffic are usually plotted from data obtained from 
the dispatcher's train sheets. These diagrams show the points 
along the line at which congestion occurs and give a much clearer 
conception of train movements than does a mass of tabulated 
information such as is found in a dispatcher's train sheet. 



CHAPTER V 
MOTOR CHARACTERISTICS! 

It will be readily recognized that the ordinary operation of a 
car, whether it be from block to block in the city or for a 5 to 10 
mile run between stations on an interurban private right of way, 
may be subdivided into periods of acceleration, constant speed 
running, coasting retardation, braking retardation, and stop. 
The conditions of particular runs as to length, grades, curves, 
etc., may materially vary or even eliminate some of these periods, 
but if all problems of car operation are to be solved, a detailed 
study of each of these portions of the so-called ''speed time curve" 
must be undertaken. 

The principal factors entering into the determination of such 
a curve will be given detailed consideration in the following order, 
the present chapter dealing only with the first two functions: 

Motor characteristics 

Gear ratio. 

Weight of car. 

Bearing and rolling friction. 

Air resistance. 

Rotative inertia of wheels and armatures. 

Grades. 

Curves. 

Brake friction. 

Motor Characteristics. — In studying the characteristics of 
motors, in order to determine those best fitted for traction service, 
it may be found convenient to classify all motors into the follow- 
ing types: 

Direct Current: 
Series, 
Shunt, 
Compound, 
Cumulative, 
Differential. 

^ See also Chap. XXII and "Standardization Rules," Trans. A. I. E. E., 
Vol. XXXlll. 

37 



38 ELECTRIC RAILWAY ENGINEERING 

Alternating Current, Polyphase: 

Induction, 

Synchronous. 
Alternating Current, Single Phase: 

Series, 

Induction, 

Synchronous, 

Repulsion. 
If the speed characteristics of all these motors be compared, it 
will be found that with varying loads within the rating of the 
motor the synchronous motors, both single and polyphase, 
maintain constant speed, while all the other direct and alternat- 
ing current motors with the exception of the series type operate 
at nearly constant speed, the speed falling off slightly, usually in 
accordance with a straight line law, as the load increases. The 
speed characteristics of the compound motor may be made to 
approximate those of either the series or shunt motors by varying 
the relative strength of the series and shunt fields respectively. 
Since with constant potential motors, particularly of the direct 
current type, the current input to the motor varies approximately 
with the load, the speed current curves of Fig. 11 may be taken 
as typical of the three classes of motors designed for commercial 
service. 

The torque of a motor, which is defined as the tangential force 
that the armature is capable of exerting at a radius of 1 ft. from 
the center of the shaft, is proportional to the product of armature 
current and field strength. Since the field strength of a shunt 
type constant potential motor is constant, the torque varies 
directly with the armature current and approximately in propor- 
tion to the load. From the above reasoning, it would be expected 
that the torque of a series motor would vary with the square of 
the current since the field current and armature current are the 
same. In the actual design of series motors for railway service, 
however, the magnetic circuit is nearly at the point of saturation 
except at very light loads. The torque current curve, therefore, 
while slightly concave upward at light loads, is nearly a straight 
line for practically all operating current values since the field 
strength varies but slightly with change of current. In Fig. 11, 
a comparison of the torque current curves of the three types of 
direct current motors will also be found. 

A study of the alternating current motors will reveal the fact 



MOTOR CHARACTERISTICS 



39 



that all types except the series have approximately the same in- 
herent characteristics as the shunt type direct current motor, 
if the starting conditions of some of the former be disregarded. 
The series alternating current motor, as constructed at present 
for railway and hoisting service, has characteristics very closely 
approximating those of the series direct current motor. 

In order to determine the best class of motor for traction pur- 
poses, therefore, it is only necessary to apply the characteristics 
of typical shunt and series direct current motors to the condi- 



















350 1200 

300 1100 
250 1000 

„ 200 c; 900 

a 














/ 




\ 








A 


^ 




\ 








/. 




-^ 


\) 


Spee< 


I Curves 


/ /[ 


V 


'•^ 









P=^ 


z 




Shunt 


150 800 
100 700 
50 600 


/y 


T-~~ 


■^^ 














Comp 


)und 




/ 


Toj 


que Cur 


^es -^ 


..^^ries 




500 




// 













25 50 75 100 125 IS'O 

Ampexes 

Fig. 11. — -Speed and torque curves of representative tj^pes of motors. 

tions of railway service. Such characteristics may be found in 
Fig. 12, where A and A' are the speed and torque curves of a 
series motor while curves B and B' represent respectively the 
corresponding characteristics of the shunt motor. The motors 
from which these characteristics were taken were designed for 
the common maximum speed of 22,8 m.p.h. with the particular 
gear ratio used. 

Tractive effort may be defined as the tangential pull in pounds 
exerted at the periphery of the car wheel. 



40 



ELECTRIC RAILWAY ENGINEERING 



It should be noted that whereas the torque curves of Fig. 11 
were plotted with values of the torque, or tangential pull at 1 
ft. radius, as ordinates, the torque of Fig. 12 is expressed as tract- 
ive effort. As it is much more convenient in applying motors 
to railway service to have the pull of the motor expressed in 
terms of tractive effort, the characteristic curves of railway 







i 




- 














1 








t 
































if 










SERIES AND SHUNT 

MOTOR CHARACTERISTICS 

FOR RAILWAY SERVICE 








il 
















y a 
































u ^^ 




























































^7 


w 




























/ 


/ 


^OUUO 




























/ 




I Miles 






















































/ 








2200 
20 

1800 
16 

U0O 






r~ 
















/ 


V 












r 












— 


— 


A 









B 






\ 














/ 
















\ 












/ 




























/ 


/ 












b; 










V 


"^ 


/ 


Y 










^ 






12 

1000 
8 

600 
4 
200 














r- 




.^^ 




^ 




















/ 






^ 


> 


< — 


-^ 






A 










/ 




^ 


^ 






















/ 




^ 
























^ 


'^ 




























/ 



























20 



60 80 100 

Amperes 

Fig. 12. 



120 



140 



motors are universally plotted in this manner. In each case, 
however, the diameter of wheels and the gear ratio involved 
must be stated, for it is evident that the same motor will give 
quite different values of tractive effort at a given current input 
if the size of wheel or gear ratio be changed. The variation of 
tractive effort of a motor for a given current with change of gear 



MOTOR CHARACTERISTICS 



41 



ratio or wheel diameter is indicated under the paragraph entitled 
''Gear Ratio." 

It will be realized at once that a car under most conditions 
found in practice must be able to operate at variable speed. 
Conditions of grades, curves, pedestrian and vehicular traffic, 




80 100 120 140 160 180 200 
Amperes 

Fig. 13. 



necessary stops, etc., demand this. Witn the geared or direct 
connection between motors and car axles usually adopted, 
therefore, a variable speed motor seems desirable. Furthermore, 
a much larger torque is required to start and accelerate a car than 
is necessary to maintain the car at full speed. As the power 



42 ELECTRIC RAILWAY ENGINEERING 

taken by a motor is roughly proportional to the product of torque 
and speed, if large values of torque cannot be obtained at low 
speeds the power taken by the motor will be excessive. Refer- 
ence to Fig. 12 will show that with the series motor a large torque 
is available at low speeds, the torque and the current as well 
falling off as the car accelerates and therefore as the demand 
for torque decreases. Assuming a concrete example, if a tractive 
effort of 1200 lb. per motor is required to accelerate a car, the 
series motor of Fig. 12 will require but 68 amp. of current while 
the corresponding shunt motor will draw 125 amp. Assuming 
that they are both operating on the same line the power demand 
in the latter case will be nearly double that of the series motor. 

For the above reasons the series direct current motor has come 
into almost universal use for traction service. During the last 
few years, however, the single phase series motor, with practically 
the same characteristics as the direct current series motor, has 
been installed in a number of instances. In many cases in 
Europe and in several instances in this country the polyphase 
induction motor has been adopted where conditions seemed to 
be particularly favorable for constant speed operation. 

Confining the discussion to series motors, the characteristics 
already considered are the torque and speed curves plotted in 
terms of current input. To these should be added the curves of 
efficiency, often plotted both with and without gears, temperature 
rise, and, in the case of alternating current motors, the power 
factor. These characteristics. Fig. 13, may be obtained either 
from design data before the motor is built or by test after its 
completion. 

Assuming that the design of a proposed motor has been tenta- 
tively made and its dimensions and winding data known, the 
speed, torque, and efficiency characteristics may be found as 
follows : 

E = Impressed voltage. 
e = Counter electromotive force. 
I = Current in amperes. 
T = Torque at 1 ft. radius in pounds. 
Ra and Rf = Resistance armature and field respectively. 
V = Speed in revolutions per minute. 
Na = Total conductors on surface of armature. 
Nf = Turns on one field pole. 
(f> = Flux per pole in maxwells. 



MOTOR CHARACTERISTICS 43 

p = Number of poles. 

6 = Number of paths in parallel on armature. 
A = Area cross section magnetic circuit at air gap. 
I = Length magnetic circuit. 
fjL = Equivalent permeability magnetic circuit. 
P = Power delivered to the shaft of motor expressed in 
watts. 

From the experimental definition of the volt: 

Na<t>pV 



60 X 1086 



(1) 



or ^ _ 60 X Whe 

but if leakage and armature reaction be neglected, 

AwNflAfx 
^ ^ 10^ ^^^ 

Substituting ^ ^ 47.7 X lO'hel 

but e = E - I{Ra + Rf) (5) 

therefore ^ ^ 47.7 X Whl[E -I {Rg -\- Rf)] 

^ NapNflAfX ^^ 

As all factors in the right-hand side of Eq. (6) are either constants 
of the design or dependent upon current, a series of assumed 
values of current will give corresponding values of speed (V) 
from which the speed characteristic may be plotted. It will 
be seen from Eq. (2) that if ((/>) be constant because of field 
saturation, the speed (V) will vary directly with the counter 
emf. (e). Since, however, the voltage drop due to resistance is 
a small percentage of the impressed voltage, it may be said that 
the speed of a series motor varies with the voltage impressed upon 
it if load conditions remain the same. This fact is of importance 
in the design of car control systems. 

With reference to the torque characteristic and neglecting iron 
losses, 

P = el (7) 

^ 2.VTX7AQ ^ 

33000 ^^ 

whence ^ ^ SSOOOel N a<i>p 

2ir X 746 X 60 X Wbe ^^^ 

or _ 0.n7INact>p 

lO^b ^ ^ 



44 ELECTRIC RAILWAY ENGINEERING 

If the flux ((/)) be assumed constant, which would be the case with 
the magnetic circuit saturated, Eq. (10) proves that the torque of 
a series motor will vary directly with the current as previously 
stated. 

While the efficiency and temperature characteristics can be 
very closely approximated in advance by means of empirical 
formulas, it is usually customary to determine these values 
roughly by comparison with other machines of similar design 
which have been previously constructed and to await the test 
for accurate results. 

Several methods of testing are available for the determination 
of all the characteristics of the motor when constructed. Three 
methods will be briefly outlined, of which the one involving the 
apparatus most available may be selected. 

Prony Brake Test. — This test is probably the simplest of 
the three and may be used where plenty of power is available 
for the operation of the motor up to 50 or 100 per cent, overloads. 
As the name implies, the motor is loaded by means of a prony 
brake from which the torque may be directly determined, while 
the current and speed are read directly by means of an ammeter 
connected in series with the motor, and a tachometer. A re- 
sistance may be inserted, if necessary, to maintain constant vol- 
tage across the motor. The efficiency curve may be obtained by 
making a series of calculations from the following formula (13) 
with varying currents. It is believed that the derivation of the 
formula is self-explanatory. 

If T' represents torque at pulley at 1 ft. radius, 

Output (hp.) = 33QQQ (11) 

Input (hp.) = ^ (12) 

Efficiency = ^f^ (13) 

Pumping Back Test. — For this test two motors, identical 
in design and construction, are necessary, but the method has the 
advantage of a relatively small power demand as the losses alone 
are supplied from outside sources. 

Two motors are placed in alignment with shafts end to end and 
mechanically clutched together. They are so connected. Fig. 14, 
that one machine, acting as a motor with a separately excited 
field, drives the other as a generator. The latter has a series 



MO TOR CHA RA C TERIS TICS 



45 



connected field. By varying the field strength (F^) by means of 
the resistance (R) the current {A') may be controlled from no load 
to overload. The output of motor No. 2, if the losses are sup- 
plied from the external source (aS), is the product of the readings 
(F) and {A'). This value of power, 

EI = ?^J<J^ (14) 



whence the torque 



r = 



33000 



33000£'/ 

27r X 746 F 



7.05EI 
V 



(15) 




Fig. 14. 



-Connections for pumping 
back test. 



Speed and torque plotted against current in amperes read from 
meter {A') furnish the two principal motor characteristics. 

In order to find the effi- 
ciency, for which a knowledge 
of the losses is necessary, the 
assumption is made that the 
combined iron and friction 
losses of the two machines are 
equal. Since the field PR 
loss of No. 2 has been elimi- 
nated from the calculation by 
the fact of its separate excita- 
tion, the losses represented by the power (AV) must be made 
up of the following: 

Friction losses of both machines. 

Iron losses of both machines. 

I^R losses of both armatures. 

PR losses of No. 1 field. 
If the resistances of both armatures and fields are known, the 
PR losses can be readily calculated for the various values of 
current. These losses subtracted from (AV) leave the total 
iron and friction losses of the two machines, one-half of which, 
according to the above assumption, is chargeable to each motor. 
Thus the losses and therefore the efficiency of the motor under 
test become known and the efficiency characteristic may be 
plotted. If a more detailed analysis of iron and friction losses is 
desired, additional tests with different connections must be 
made.^ 

The two temperature curves of Fig. 13, showing respectively 

^ See "Experimental Electrical Engineering," by V. Karapetoff, pp. 
406-407. 



4:6 ELECTRIC RAILWAY ENGINEERING 

the time required for the motor to rise 75°C. above the room 
temperature when starting cold and the time to rise 20°C. above 
the temperature of 75°C. for the various currents in the motor 
circuit, are of the greatest value not only in selecting the proper 
motor for a given service, but for determining the tempera- 
ture rise corresponding to various overloads which the motor 
will usually be called upon to carry for short intervals of time. 
The values from which these curves may be plotted can best be 
obtained by actual test preferably with the connections of Fig. 14, 
separate runs being made, of course, for each value of current. 
Thermometers placed on the various parts of the machine during 
the run indicate when the desired temperature has been reached 
and the time for such rise may then be plotted against the con- 
stant value of current maintained during the test.^ Additional 
thermometers may be applied to determine the temperature of 
rotating parts at the end of the test and the hot resistance of the 
windings taken to determine by calculation the internal tempera- 
tures of the coils. 

Test Using One Motor as a Generator. — In this case the 
motors are mechanically clutched together as in the "pumping 

back" test, one being used as 

^ ^ ^^ f1 a motor to drive the other as 





R 



a generator. The latter is 
loaded by means of a water 
rheostat as shown in Fig. 15. 

Fig. 15.-Connections for motor used The calculations for losses and 
as generator. efficiency are very similar to 

those in the previous test, 
this method differing from the former principally in the type 
of load used. These connections are often used by the manu- 
facturing companies for the 1-hour heat run usually applied to 
railway motors. 

Gear Ratio. — Since a suitable design for a railway motor de- 
mands a speed much higher than that at which the car axle should 
be driven in ordinary installations, single reduction gearing is 
introduced between the motor shaft and the car axle, a pinion 
upon the former engaging a gear keyed to the latter. 

It has become customary in railway practice to express this 

gear ratio as an integer, or 

^ ,. No. teeth in gear ,^-x 

Gear ratio = - ^t — 7t~^ . ■ (lb) 

No. teeth m pmion 

iSee "Rating," Chapter XXll. 



MOTOR CHARACTERISTICS 47 

As it is most convenient to plot the characteristic curves of 
railway motors in terms of forces at the periphery of the car wheel 
and speeds in miles per hour traveled by the car, it is obvious 
that a given group of such curves is dependent upon a single 
definite car wheel diameter and gear ratio. With a change of 
gear ratio, however, the motor speed remaining the same, the 
speed of the car will change in the inverse proportion while the 
tractive effort will, of course, vary in direct proportion to the 
change in gear ratio. 

The torque and speed characteristics may, therefore, be 
changed to appl}^ to a new gear ratio by the use of the proportions 
given in equations (17) and (18). 

New speed Old gear ratio 



Old speed New gear ratio 
New tractive effort New gear ratio 



(17) 
(18) 



Old tractive effort Old gear ratio 

Motor characteristics thus changed are represented by the 
dotted Unes of Fig. 13. 

Since the tractive effort increases and the sj>eed decreases for 
a given current as the gear ratio is increased, it is clear that more 
rapid acceleration may be obtained with a given equipment with 
greater gear ratios. Where frequent stops are necessary and 
the equipment can maintain schedule speed without difficulty, 
the question of possible increase of gear ratio may be studied 
to advantage. 

More than this, if the required tractive effort can be maintained 
wdth a reduced current by increasing the gear ratio and if the high 
speeds obtainable with a low ratio are not required to make 
schedule time, a very material decrease in the power taken by 
the car or train may often be secured by more careful selection 
of gears. 

A concrete example of the acomplishment of both of the pre- 
ceding improvements is indicated in the following test: 

Gear ratios 



3.58 I 4.12 



Stops per mile (average) , 
Schedule speed, m.p.h. . . 
Watt hours per car mile . 
Watt hours per ton mile . 




48 ELECTRIC RAILWAY ENGINEERING 

An increase was made in the number of stops in this case with 
but sHght decrease of schedule speed, while the power taken by 
the car was materially reduced. In many such instances a care- 
ful selection of the proper gears will result not only in better 
service but in less operating cost as well. 



CHAPTER VI 

SPEED TIME CURVES (COMPONENTS) 

Weight of Car. — From the familiar relation Force = Mass X 
Acceleration expressed in the formula 

F = ma (19) 

it is clear that the weight of the car, complete with its equipment 
and load, will enter into the calculations for the speed time curve 
as an important factor. The above equation may, however, be 
reduced to a form more convenient for railway application as 
follows : 

m = w/g (20) 

where (w) represents the weight in pounds and (g) the accelera- 
tion of gravity (32.2). Eq. (19) becomes with this substitution 

^ = 3^2 (^1) 

Changing to the more convenient units of miles per hour in place 

of feet per second by means of the constant 1 m.p.h. = ^^tjt: = 

1.467 ft. per second or (a) = 1.467 A, when (A) is expressed in 
miles per hour per second, and substituting 2000 W in place of 
(w) expressed in pounds, Eq. (21) becomes 

^ WAX 2000 X 1.467 



32.2 



= 91.1 WA (22) 



In order, therefore, to accelerate a car at a rate of 1 m.p.h. 
p.s., a net force of 91.1 lb. must be exerted for every ton weight 
of car. It must be remembered that this net force available 
for acceleration is only that which remains after all resistances 
to the motion of the car have been overcome. 

It is now possible to obtain a relation between the tractive effort 
of the motors comprising the car equipment and the acceleration 
that this tractive effort will produce for a given weight of car. 
4 49 



50 ELECTRIC RAILWAY ENGINEERING 

This will obviously depend upon whether a two or four motor 
equipment is used. Eq. (22) may be written 

if n = number of motors on car, 
Pm= net tractive effort per motor. 

From the above equation it will be seen that the acceleration is 
inversely proportional to weight of car. 

Bearing and Rolling Friction. — In studying the various re- 
tarding forces which have to be overcome by the motors in car 
operation and which must, therefore, be subtracted from the 
gross tractive effort of the motors in order to determine the net 
effort available for acceleration, it seems logical to consider first 
those forces acting under the normal conditions of a straight level 
track. Among these forces are found the friction of armature 
and axle bearings. The axle friction, which is usually the greater 
of the two, varies with the pressure on the bearing and therefore 
with the weight of the car for a given truck arrangement. Both 
frictional resistances vary very nearly in proportion with the 
speed. In building up an empirical formula for train resistance, 
therefore, expressed in pounds train resistance per ton weight of 
car, it would be expected that bearing friction would be repre- 
sented therein by a constant term added to a term varying with 
speed. 

There are found to be present, however, in the operation of a 
car other frictional forces exerted between the wheels and rails. 
These forces have been termed ''rolling friction." They are 
caused partly by the rubbing of the wheel flange against the head 
of the rail and partly by the fact that there is apparently a slight 
depression in the rail under each wheel out of which the wheel 
must be forced against an appreciable resistance. This effect is 
more marked with a greater distance between ties or in cases 
where rail spikes have become loosened, allowing considerable 
vertical motion to the rail as the car passes over it. Since the 
flange friction previously mentioned is considerably increased if 
the track gauge is not maintained constant, the entire item of roll- 
ing friction may vary greatly with the condition of the track. As 
this resistance will also vary with the speed and weight of the car 
for a given track, both bearing and rolling friction may be repre- 
sented by a single constant plus a second term varying with speed. 



SPEED TIME CURVES 



51 



Air Resistance. — The amount of resistance offered to the 
motion of the car by the air is very surprising, especially in the 
case of single cars at relatively high speeds. Not only is con- 
siderable resistance offered to the front cross section of the car as 
it cuts through the various strata of air, but the friction of the 
air upon the sides of the car and the eddies and suction produced 
at the rear cause a considerable retarding effect upon the motion 
of a train. This suction phenomenon may readily be observed 



90 










TRAIN RESISTANCE CURVES. 








85 








25 TON CAR WITH VARYING SPEED 








80 












^/ 


/ 




/ 


/ 






/ 


^ 


75 












f 




# 


/ 




y 


y 






70 












/ 




^/ 


r 


^^ 


f 


/* 








65 
60 

^'50 

Cl 










/ 


/ 


/ 


/ 


/ 


y 




















/ 




/ 


/ 


/ 








\ 


0> 


^ 








/ 


f 


/ 


/ 


/ 








x^ 


■^ 












/ 


/ 




/ 








y- 








|io 

CO 






/ 




/ 








y 


y 
















/ 


/ 


/ 






/ 


/ 














35 
30 
25 
20 
15 
10 






/ 1 


> 


/ 




/ 


/ 


















/ 


/ 


/ 




A 


/ 




















/ 


// 


f 


/ 


/ 






















// 


/ 




/ 
























7 


/ 


/ 


























// 


f 


/ 
























5 




/ / 




1 

























10 15 20 25 30 35 

Train Resistance in Lbs. per Ton 
Fig. 16. 



iO 



at the rear of a high speed train by noting the motion which it 
conveys to cinders and light objects found along the track. 

This air friction upon the various portions of the car has been 
more or less successfully measured in train resistance tests, but 
there still exists a wide difference of opinion regarding its abso- 
lute value. It is generally conceded, however, that the front 
and rear end resistances are proportional to the cross-sectional 
area of the car from car axle to roof and that the side resistance 
of a single car is approximately one-tenth of the sum of head and 
rear resistances. Since the side resistance is much smaller than 



52 



ELECTRIC RAILWAY ENGINEERING 



the end resistance it would be expected that the total air resist- 
ance per ton weight of car would be very much greater for a 
single car than for a train. This has been found to be so marked 
in the tests carried out that it is usually impractical to operate a 
single car much over 60 m.p.h., while a train of many cars 
may be operated at much higher speeds without serious loss. 
While this air resistance is a comparatively small quantity at 





































TRAIN RESISTANCE CURVES. 

SINGLE CAR OF VARYING WEIGHT 

AT CONSTANT SPEED. 














































































































































' 


\ 










\ 




















\ 










\ 


s. 




















\ 










\ 


















\ 


\ 












\ 


■ 














\ 


\ 


^ 












\ 














\ 




\ 














X 


^^ 


r> 










\ 


\ 


\, 
















^ 


^ 








\ 




\ 


s 


























\ 




\ 


X 


S-r 1 
























\ 






<^ 


^. 






















^ 


r^ 


tf^ 


H. 











































10 15 20 25 30 35 

Besistance in Ebs. per Ton 

Fig. 17. 



40 



l6w speeds, it is generally considered to vary with the square 
of the speed and is therefore a very formidable factor at high 
speeds. 

As a result of the various train resistance tests which have been 
made by determining the retardation of cars and trains while 
coasting from different initial speeds to a standstill on a straight 
level track, a number of empirical formulas have been suggested 
and used with varying degrees of accuracy in train calculations. 
The tests which have been made comparatively recently with 
electric equipment, with which the power is much more accurately 



SPEED TIME CURVES 53 

measured than in steam locomotive tests, may be represented by 
the cm-ves of Fig. 16, plotted in pounds per ton train resistance 
for 25 ton cars against' speed in miles per hour. This train 
resistance includes bearing and rolling friction and air resistance 
upon the entire car or train. 

The empirical formula from which these curves were plotted 
and which probably approximates most closely the true train 
resistance in practice of short, high speed trains is represented 
below : 

•/=^ + »-- + T-('+'t) <-) 

/ = Total train resistance in pounds per ton weight of train-. 
W = Weight of train in tons. 
V = Speed of train in miles per hour. 
a = Area of cross section of front end of car or locomotive 

above axle expressed in square feet. 
n = Number of cars in train. 

In this formula the first two terms express the rolling and bear- 
ing friction while the last term determines the resistance due to 
air friction and suction. 

The effect of increased weight of cars upon train resistance at 
constant speed is very clearly shown in the curves of Fig. 17, 
which are plotted from the same formula. It must be remem- 
bered that this effect is entirely separate from the extra tractive 
effort necessary to accelerate the heavier cars and therefore 
represents an additional negative force or resistance which the 
motors are called upon to overcome when operating heavy 
rolling stock. 

Rotative Inertia of Wheels and Armature. — It will be re- 
membered from mechanics that if two different rotating masses 
of different inertia are acted upon by similar propelling and 
similar resisting forces respectively, the mass having the greater 
inertia will have the lower value of acceleration or retardation 
as the case may be. 

. From this fact it would be expected that the relatively large 
inertia of the rotating elements of the car, including motor arma- 
tures, gears, pinions, axles, and wheels would tend to reduce the 
acceleration when the car is starting and the retardation when 
coasting and braking. This inertia factor must be taken into 
^ See ''Electric Traction," by A. H. Armstrong. 



54 ELECTRIC RAILWAY ENGINEERING 

consideration in the accurate calculation of speed time curves as 
follows : 

The energy of rotation — 

E=f = Mfl (25) 

since 

/ = Mk^ (26) 

where oj = Angular velocity. 
/ = Moment of inertia. 

M = Mass. 
k = Radius of gyration. 

These fundamental formulas will be applied to this particular 
problem with the following nomenclature: 

nw = Number of pairs of wheels on car. 
Ua = Number of armatures on car. 
Ww = Weight of each pair of wheels and axle in tons. 
Wa = Weight of each armature in tons. 
kw = Radius of gyration of wheels and axle. 
ka = Radius of gyration of armature. 
r = Radius of wheels in feet. 
A = Acceleration of car in m.p.h./sec. 
V — Velocity of car in ft. per sec. 
V = Velocity at extremity of radius of gyration. 
g = Acceleration of gravity. 
G = Gear ratio. 
W = Weight of car in tons. 
p = Net tractive effort at periphery of wheel. 
Considering first the wheels and axles: 
From Eq. (25) 

(28) 



But 


2g 




kw<^ = V 


Substituting 





(29) 

Since the velocity of the periphery of the car wheel is the same 
as that of the car, if it be assumed that no slipping occurs, 

£» = «»5'(t'^')' (30) 



SPEED TIME CURVES 55 

or, in other words, replace nu,Wu, with the equivalent weight 
ny,Wu- if (V) is used in (29). 



m 



In a similar manner, remembering that in transferring armature 
values to those at the periphery of the wheel the gear ratio (G) 
must be introduced 



£a = ««|^(7Gr)' (31) 



~Gj riaWa. 

By adding the new values of equivalent weight, expressed in 
tons, necessary to overcome rotational inertia, therefore, formula 
(22) may be corrected to read 

F = 91. L4 [n^ + n..TF. (^) ' + riaWa (^) '] (32) 

Since the radius of gyration 

and all revolving parts to be considered in electric traction may 
be assumed to be cylinders revolving about their axes, 

/ = M J ' (34) 

fc = :^^ (35) 

In order to determine approximately the magnitude of the 
inertia of rotating parts the following concrete values, which are 
often found in practice, may be assumed. 

= 4 

= 0.75 ton 
= 0.35 ton 

= 1.375 ft. 
= 0.97 ft. 
= 0.412 ft. 

= 2.74 



riy, 


= ria 


Wu, 


= 1500 lb. 


Wa 


= 700 lb. 




33 in. 


r 


~ 2X 12 


1 


33 in. 


Kyj 


"" 2 X 12\/2 


K 


14 in. 


~ 2 X I2V2 


A 


= 1 m.p.h./sec, 


G 


= 19/52 


W 


= 25 tons. 



56 



ELECTRIC RAILWAY ENGINEERING 



Substituting in (32) 

F = 91.1(25 + 1.49 + 0.944) = 2500 lb. 
or 100 lb. per ton. In other words, the net tractive effort 
necessary for translation must be increased approximately 9.8 
per cent, for this car in order to overcome the inertia of rotating 
parts for an acceleration of 1 m.p.h./sec. 

For approximate calculations, 100 lb. per ton is often as- 
sumed for the net tractive effort without calculation of rotative 
inertia. The following table taken from the Standard Handbook 
will give other values which may be assumed under varying 
conditions. 

Table VI. — Per Cent, of Total Tractive Effort Consumed in 

Rotating Parts 

Electric locomotive and heavy freight train 5 per cent. 

Electric locomotive and high speed passenger train. . . 7 per cent. 

Electric high speed motor cars 7 per cent. 

Electric low speed motor cars 10 per cent. 

Grades. — Whenever a grade is encountered it is not only 
necessary to provide an additional tractive effort to overcome 




Fig. 18. — Forces existing as result of grades. 

linear and rotational inertia, but it is also necessary to make use 
of some of the tractive effort of the motors in actually lifting the 
car through the vertical distance represented by the grade. In 
other words, referring to Fig. 18, the weight of the car (W) may 
be resolved into the two forces (N) and (W sin a) which are 
normal and parallel to the track respectively. The reaction of 
the track balances the former while a force' proportional to the 
latter must be supplied by the motors of the car. As the angles 
(a) and {a') are equal it is obvious that this force is proportional 
to the grade and amounts to 0.01 X 2000 = 20 lb. per ton weight 
of car for each per cent, of grade. If the car is on a down grade 
this force is available for producing acceleration and is therefore 
added to the tractive effort of the motors. 



SPEED TIME CURVES 



57 



The ruling grade of a road is that grade which Hmits the weight 
of the train or car to be operated upon a given schedule. It is 
not necessarily the steepest grade upon the road, for the momen- 
tum of the train may often be sufficient to prevent a short steep 
grade which is advantageously located from becoming a determin- 
ing feature in the weight of train for a desired schedule. The 
ruling grade can be determined only by careful calculation of oper- 
ating characteristics upon all large grades on the road or by actual 
test runs over the road with trains of varying weight. 

Curves. — Before it is possible to consider the resistance offered 
to the passage of a car or train by curves in the track, it is neces- 
sary to understand clearly the method of rating curves. In city 
streets where sharp curves are met with they are usually desig- 
nated by their radii, e.g., a curve of 30 ft. radius. On private 




Fig. 19. — Track curve diagram. 

rights of way, however, in suburban and interurban construction, 
it has been customary to designate curves in degrees of central 
angle subtended by a chord of 100 ft. Referring to Fig. 19, if 
angle (0) is drawn so that it is subtended by the chord (ac) of 
100 ft. and (0) = 1°, then the radius (Oh) necessary to make 
this assumption correct is found as follows: 



tan 30' = 0.0087 



50 

(05) 



or {Oh) = 5730 ft. 



The radius of a 1° curve is therefore 5730 ft. 

If now (ab) be moved toward (0) such a distance as to make 

(Oe) = (eb) 

50 



tan 



2 2865 
Therefore, curvature in degrees = 



0.0175 = tanror^ = 2° 
5730 



radius 



58 ELECTRIC RAILWAY ENGINEERING 

As a car enters a curve there is, of course, a tendency to ride 
over the outer rail and there occurs between the flange of the car 
wheel and the head of the rail considerable frictional force 
tending to cause the car to follow the rail but at the same time 
retarding the motion of the car. This force must be considered 
as an additional resistance which manifests itself in frictional 
heat. 

The amount of this resistance has been approximated from 
test data and it is conceded that it is directly proportional to the 
curvature in degrees. Values ranging from 0.52 lb. to 1 lb. per 
ton weight of car per degree curvature have been obtained, but 
good practice at present stipulates 0.6 lb. per ton weight of car 
per degree curvature. When the car is on a curve, therefore, an 
additional force of 0.6TF X degrees curvature must be subtracted 
from the gross tractive effort in addition to all resistances pre- 
viously considered. 

Probably the best method of summarizing the discussion of 
train resistance is to express in terms of a formula the derivation 
of the net tractive effort available for acceleration from the 
gross tractive effort obtained from the motors, thus — 



where 



P =P -f±g -c (36) 

P = Gross tractive effort of motors in pounds per ton. 
p = Net tractive effort available for acceleration in 

pounds per ton. 
/ = Train resistance due to bearing and rolling friction 

and air resistance in pounds per ton. 
g = Resistance due to grades in pounds per ton. 
c = Resistance due to curves in pounds per ton. 

The use of this net tractive effort (p) in calculating the accel- 
eration of a car or train will be discussed in detail in the following 
chapter. 



CHAPTER VII 
SPEED TIME CURVES (THEORY) 

Having considered in detail the various factors entering into 
the speed time curve, the methods of plotting same may now be 
considered. Two methods are in general use, the so-called ''cut 
and try" method which involves considerably more time for its 
performance but which is the more accurate, and the ''straight 
line" method which assumes all portions of the diagram made 
up of straight lines, thereby simplifying the calculation at the 
expense of the introduction of slight errors. The former and 
more accurate method will first be considered, for only through 
the complete analysis of the correct curves can a thorough 
understanding of electric car performance be obtained. 

The distance between the two consecutive stops having been 
determined, it is next necessary to select the proper schedule 
speed for the run, i.e., the average speed which if maintained 
constant throughout the run would bring the car to its destina- 
tion in the required time. This speed is usually determined from 
trafl&c studies and is, of course, dependent upon the train 
schedule of the entire system. With the distance and schedule 
speed determined, the time required for the run can be calculated 
and the limits of the curve laid off graphically to scale as (OT) 
in Fig. 20. 

The nomenclature which will be used is as follows: 

T.E. = Gross tractive effort per motor in pounds. 

P = Gross tractive effort at periphery of car wheel in 

pounds per ton. 
p = Net tractive effort in pounds per ton. 
V = Speed corresponding to {T.E.) in m.p.h. 
/ = Current corresponding to {T.E.) in amperes. 
A = Acceleration in m.p.h. /sec. 
D = Retardation in m.p.h. /sec. 
V = Average speed in m.p.h. 
S = Length of run in feet. 
s, s', etc. = Distances in feet. 

T — Time for entire run in seconds. 

50 



60 



ELECTRIC RAILWAY ENGINEERING 



t, f, etc. = Time for portions of run in seconds. 
/ = Train resistance in pounds per ton. 
g = Grade resistance in pounds per ton. 
c = Curve resistance in pounds per ton. 
h = Braking resistance in pounds per ton. 
W == Weight of car in tons. 
n = Number of motors on car. 
TFi = Weight of car per motor in tons. 

































^ 


^ 


f "~ 
































/ 


-$■ 


































/ 






























^ 


-^ 


*' 


/ 














30 






















/ 






r 
















^J^- 


^ 










/ 








\ 

\ 










25 






■f 


1 




^- 






/ 












\ 












A 


1 

1 




N 


\ 
v 


/ 














\ 

\ 








20 




67 


1 


1 

1 






/ 




K-J 












\ 
\ 










1 


1 
1 


1 

1 




/ 


/ 




"N 


\: 


^\ 








\ 

\ 








15 




\ 


1 
1 


1 

1 




/ 










< 


\ 
\ 


-■s 




\ 
\ 










/ 1 

f 1 


1 
1 


1 

1 


/ 
















^ 


f:- 


\ 








10 


/ 


1 


1 

1 


1/ 


/ 


















v. 


<^ 


vl 






/ 


1 

1 


1 
1 


i 
























\ 


^x 


k 


5 


/ 


1 


/ 


1 

1 
























\ 






/ 


n'y 


/I 
1 


1 
1 
























\ 








/ 


4 


,1 

0\<) 


1 

'1 


























T 





4000 



3500 



3000 



2500 1; 



2000 ^ 



1500 



1000 



500 



10 20 30 40 50 



70 80 90 100 110 120 130 140 150 160 
Time in SeGonds 
Fig. 20. — Speed and distance curves. 



Referring to Fig. 20, 

OT =T 



5 



(37) 



7 X 1.467 

The acceleration (A) must be assumed sufficiently large to 
enable the desired schedule to be made and yet not so great as 
to be of inconvenience to passengers. Values may be taken from 
Table VII for the class of service under consideration. The 
method of calculating the net tractive effort (p) has been pre- 
viously explained in formulas and it will therefore be considered 
as a known quantity. 



SPEED TIME CURVES 61 

Table Vll. — Acceleration Rates 



Type of service 



Acceleration in 
m.p.h./sec. 



Electric passenger locomotives . 

Interurban cars. 

City cars 

Highest practicable rate 



0.3 toO.6 
0.8 to 1.3 
1.5to2.0 

2 . to 2 . 5 



The gross tractive effort per ton may now be found: 

P = {p+f±g-^c) (38) 

The sign of the grade resistance (g) depends, of course, upon 
whether the car is ascending or descending the grade; in the 
latter case the sign is negative and the gross tractive effort 
necessary is decreased by the presence of the grade. 

The weight of car which must be accelerated by each motor is : 

W 

W. = - (39) 

The gross tractive effort which the motor must exert is, therefore: 

T.E.=PW, = '^{p+f±g + c) (40) 

Referring to the characteristic curves of the motor which has 
been assumed as probably of the correct design for this service 
the gross tractive effort (T.E.) is found to correspond to a current 
/ {Oa, Fig. 21) and at this current the speed is v {ah, Fig. 21). 
The motors of the car will be able to maintain this rate of accel- 
eration (A) as long as they can be supphed with current I = Oa. 
As the speed increases, however, the current and therefore the 
tractive effort will decrease unless the voltage applied to the 
motors is increased. This is the function of the control equip- 
ment whether it be of the rheostatic, series parallel, or auto-trans- 
former type. Until such time as the voltage impressed upon 
the motors reaches the maximum value possible with the par- 
ticular control equipment in use the assumed value of accelera- 
tion (A) may be used for calculation. In other words, the ac- 
celeration portion of the speed time curve may be drawn as a 

straight line from with a slope of i-r = A\ until a speed is 

reached corresponding to {v = ah), Fig. 21. This line is drawn 
as Oh' in Fig. 20 where a'h' = ah. Fig. 21. 



62 



ELECTRIC RAILWAY ENGINEERING 



Beyond the point Q)') the ''cut and try" method using incre- 
ments of speed and time must be used. The time, t = Oa' corre- 
sponding to point h', can readily be calculated from the equation 

* = Z = ^ (41) 

Assuming a small increment of speed beyond point Q)') = dv, 
the new speed is (v + dv) = ec. Referring to the characteristic 



30 



25 



20 






10 



SPEED AND TORQUE CHARACTERISTICS 

OF WESTINGHOUSE NO. 56-500 VOLT MOTOR 

50 AMP., 300 VOLTS' 

46 AMP., 400 VOLTS 




4000 
3500 
3000 
2500 
2000 
1500 
1000 
500 



20 40 60 80 100 120 140 160 180 200 
Amperes 
Fig. 21. 



curves (Fig. 21), this speed (ec) corresponds to a gross tractive 
effort T.E/ = (ef). It is now necessary to determine what ac- 
celeration this tractive effort can produce as follows: 

T.E/ 



Net tractive effort p' = 



W 



-f ±g'-c' 



(42) 



If the speed increments are selected sufficiently small the 
value of (/') will not be materially different from (/), although for 



SPEED TIME CURVES 63 

accurate work substitution should be made of the resistance from 
the train resistance curves, Fig. 16, for the average speed repre- 
sented by the increment (dv). The distance curve explained 
below will determine the portions of track corresponding to 
various points on the speed time curve, thus permitting correct 
values of (g) and (c) to be selected. In many cases these latter 
values do not change materially throughout the calculation. 
Having determined the new value of net tractive effort (pO> 

A' = ^A (43) 

P 

where (A') is the new acceleration for the increment of speed (dv). 
The time required to traverse the distance (ds) may be calculated 
from the equation 

dt = ^ (44) 

The coordinates of the next point upon the acceleration curve 
are therefore known to be (v + dv) = g'h" and {t + dt) = Og' , 
and the point may therefore be plotted as (?)'')• 

If this procedure be continued, assuming new increments of 
speed and calculating the corresponding values of the time 
increments, the complete acceleration curve may be plotted. 
This curve will become horizontal when the acceleration reaches 
zero; or, in other words, when the gross tractive effort of the 
motors is completely balanced by the resistances so that no net 
tractive effort remains to produce acceleration. With no change 
in grade or curvature of track the car will continue running at 
constant maximum speed until the power is shut off. 

Coasting. — The amount of coasting permissible in a given 
run varies widely. In some instances where schedules are very 
conservatively planned and the equipment more than adequate 
for the demands made upon it, excessive coasting is introduced, 
while in heavy suburban and elevated service, braking is often 
begun as soon as power is shut off, the coasting portion of the 
curve being entirely eliminated. In order to be able to make up 
time in case of delay, however, some coasting should be provided 
for in the speed time curve, the time involved in this portion of 
the run acting as a storage reservoir for a hydraulic plant since 
it may be drawn upon if necessary to maintain normal schedules. 

In order to plot an absolutely accurate coasting curve the 
"cut and try" method should be used, since the average speed 



64 ELECTRIC RAILWAY ENGINEERING 

during the coasting period, from which the train resistance factor 
(/) is obtained, is difficult to predetermine, and for the further 
reason that the resistance (/) does not vary directly with the 
decrease in speed. It is customary, however, to consider the 
coasting portion of the diagram as a straight line, i.e., to assume 
the retardation constant, and to select the value of (/) from appro- 
priate resistance curves (Fig. 16) for an approximate average 
speed during coasting, or even to assume (/) directly. This value 
is often taken arbitrarily at 15 lb. per ton. 

With the value of (/) known, the retardation is 

^„^ -(/±^ + o) ^ (45) 

from which the increment of time {dt) corresponding to an 
assumed change of speed {dv) may be calculated as follows: 

* = S (46) 

The coasting line may then be drawn through (/'), Fig. 20, 

dv 
with a slope Dc = -n- Such a line is (fk), Fig. 20, (/') being 

any point arbitrarily selected upon the acceleration curve. The 
line (fk) determines the slope but not necessarily the exact 
position of the coasting line. 

Braking. — Since the speed time curve must cut the time axis 
at T, Fig. 20, in order that the run may be completed in the pre- 
determined schedule time, the braking line can best be drawn 
back from T, the slope being determined by the assumed brak- 
ing retardation as in the case of the coasting curve. As in the 
case of acceleration, this rate must be selected sufficiently high to 
enable the schedule to be maintained and yet not prove dis- 
agreeable to passengers. In heavy suburban and elevated traffic 
where speed is relatively high and headway short the braking 
rate must necessarily be high. Braking rates as high as 2.5 
m.p.h./sec. may be attained in extreme cases with high speed 
passenger trains, although rates for freight trains do not exceed 
0.7 to 0.8 m.p.h./sec. An average figure often assumed is 1.5 
m.p.h./sec. The braking line in Fig. 20 is represented by Tr\ 

The area under the speed time curve obviously represents the 
distance traveled during the run. In plotting the curve, there- 
fore, especially if the distance time curve is not simultaneously 



SPEED TIME CURVES 65 

plotted, it is advisable to determine the area of the diagram occa- 
sionally by means of a planimeter as a check upon the distance. 
In closing the diagram, also, after the braking line has been 
drawn, the coasting line (Z'm') must be so located parallel to (fk) 
that the area of the diagram will correspond to the distance 
traveled between the stops under consideration. The comple- 
tion of the diagram is therefore a ''cut and try" method. 

In order that this method of plotting speed time curves may be 
more clearly understood a concrete example of a typical problem 
will be found in Chap. IX. 



CHAPTER VIII 

DISTANCE, CURRENT, AND POWER TIME CURVES 

(THEORY) 

The speed time curve having been determined, the second- 
ary curves which are dependent thereon may now be given 
consideration. 

Distance Time Curves. — The distance time curve which is 
usually plotted simultaneously with the speed time curve is also 
obtained by the ''step by step" method, the series of increments 
of time determined for the speed time curve together with the 
corresponding average speeds during the increment being used to 
calculate the increments of distance as follows: 

ds = ^^i±^ X lAQldt (47) 

These increments of distance when plotted form the curve 
iPn'y'), Fig. 20, having ordinates expressing distance in feet cor- 
responding to abscissae of time in seconds. Such a curve rises 
slowly as the speed increases, maintains a constant slope, and 
gradually approaches the horizontal during the coasting and 
braking periods. 

Current Time Curve. — In order that the power which will be 
taken by a car on a given run may be predetermined the current 
and voltage time curves must be plotted. Since the voltage is 
usually assumed constant at some average value which may 
reasonably be expected to obtain over the entire line, its graph- 
ical representation is merely a straight horizontal line. 

With the current, however, it will be remembered that the 
control equipment is expected to maintain practically constant 
current values in each motor until the net tractive effort falls 
below that necessary for the initial assumed acceleration. This 
point, which is represented by (6'), Fig. 20, has its time coordi- 
nate definitely fixed. The current per motor (/), as found from 
the characteristics for this particular speed, might be plotted as 
constant from the start to a point {t = oa'). Since, however, the 

66 



DISTANCE, CURRENT, AND POWER TIME CURVES 67 

series parallel control is ordinarily used and the current con- 
sumption for two motors is the important consideration, it is 
usually assumed that during the first half of the time (oa'), Fig. 
20, the motors are in series and during the latter half period in 
parallel. The current consumption for two motors is, therefore, 
double the value in the latter or parallel half that it is in the 
first or series half of the constant acceleration portion of the run. 
Thus two of the motors of a four motor equipment would have a 
current time curve during the constant acceleration period rep- 
resented by (OO'afg) , Fig. 22, while the current of all four motors 
or, better, the current per car for the same period may be deter- 



















CURRENT TIMECURVES 














s 




















































































360 












































k 




b" 














. 




■->s. 
















320 
280 
240 
200 














\ 








^ 


^ 








\ 


\ 




















\ 


\ 


















s 


\, 




















\ 


, / 


















s 


\ 










o" 


_i 




.0 




X 






















V 




n 




160 
120 

80 








\ 


\^ 


































o' 


( 






X 


v^ 






■ 










































































a" 








i 


' 






















9" 





5 10 15 20 25 30 35 40 45 50 55 80 65 
Time in Seconds 
Fig. 22. 



rO 75 80 85 90 95 100 



mined at any instant from the curve {00" jW) of the same 
figure. Since the two sets, of two motors each, are in parallel 
with each other the total current per car in the series connection 
{00") is double {flO') and the corresponding ''parallel" current 
{a"h") is double {00"). 

Beyond the point 6", because of the increase of speed, the 
current begins to decrease, each point on the curve being readily 
determined by referring back to the motor characteristic curve, 
Fig. 21, for the current values corresponding to the various 
coordinates of speed and time on the speed time curve. The 
complete current curve up to the time (ogO? Fig. 20, where the 
current is shut off, may then be plotted as {00"fkh"lq'), Fig. 22. 



68 



ELECTRIC RAILWAY ENGINEERING 



Power Time Curve. — The power taken at various times 
during the run can be very readily represented graphically with 
the same abscissae as the above current curve but with ordinates 
which are the products of the current curve ordinates and the 
average assumed voltage. Since the voltage is constant, the 
power diagram (OiOi'fikibi'liqi), Fig. 23, will take the same 
form as the current curve. 

If alternating current series motors are being considered, with 
which the series parallel control is seldom used, the current per 
motor and also per car will remain fairly constant throughout the 
constant acceleration period, ^.e., during the time {Oa"), Fig. 22. 



















POWER TIME CURVES 
































AVERAGE VOLTAGE 500 
















180 




















































































h 




J\ 












^ 




-^ 


N, 






















\ ' 


140 








\ 








/ 


^ 








\ 


\ 




















\ 






/ 


/ 












s 


s. 












100 










\ 


/ 


/ 
















s 


\ 










o': 


/• 








^ 


1:;^ 




















\ 




n. 










60 




■> 












^' 




















































. 


















20 












































0, 














q 


: 






















q,, 





10 



80 



30 



40 50 60 

Time in Seeonds 

Fig. 23. 



70 



90 



100 



Since the voltage impressed upon the motors during this period is 
usually varied by means of an auto-transformer or induction 
regulator, neither of which involves the power losses incurred by 
the direct current rheostatic and series parallel control systems, 
the voltage curve is assumed as a straight line between the starting 
voltage and maximum operating secondary voltage. This start- 
ing voltage, or the voltage necessary to produce the initial tractive 
effort, may be determined from motor tests, while the maximum 
operating secondary voltage is usually that at which the motors 
are designed to operate. 

If the product of the ordinates of the current and voltage 
curves for each of the time increments be plotted to a scale re- 



DISTANCE, CURRENT, AND POWER TIME CURVES 69 

duced in the ratio of 1000 to 1, a kilo volt-ampere curve results 
which is quite as useful in determining substation and distri- 
bution system requirements as the kilowatt curve. Fig. 24 
illustrates such a kilovolt-ampere curve for a proposed inter- 
urban line operating 72 ton, 2 car trains, made up of a 44 ton 
motor car and a 24 ton trailer with rotative weight of 4 tons, 
equipped with four 125 hp., 200 volt, 25 cycle single-phase al- 
ternating current series motors with a 2.33 gear ratio. 

Whereas the kilovolt-ampere time curve is of great value as 
explained above, it is usually necessary to know the actual power 
consumption expressed in kilowatts at any time during the run. 



700 






















1 1 1 






































1 






















600 








' 


KILOVOLT AMPERE AND KILOWATTTIME CURVES 
ALTERNATING CURRENT SINGLE PHASE MOTORS 






















-^"500 
> 












































_L i\l 










































-giOO 




w 














































\\ 














. 




























^300 




^ 


N> 


V 










































\ 


*^ 


•^ 








i 
K.V. A 




































^~-»,^ 




1 1 














. 


200 








K.\V. 1 




















































100 






























































































































Coast 






Brake Sta. 
^top.. Stop 







4. 





8 





1^ 


!0 


16 


)0 


2C 
T 

Fi 


K) 
ime 

G. 


2J 
in 

24 


to 
Sec 


2J 
ond 


s 


3; 


>0 


3t 


)0 


4C 


Ki 


4- 


10 



This is rendered possible by plotting the kilowatt time curve, 
Fig. 24, which is related to the kilovolt-ampere curve at any in- 
stant by the expression 



Kilowatts = kilovolt-amperes X power factor 



(48) 



Reference to Fig. 131 will show that the power factor of an 
alternating current railway motor varies with the current. In 
order to fix accurately a point on the kilowatt time curve of Fig. 
24, therefore, it is necessary to select a given instant of time, find 
the current in the motor at that instant from the current time 
curve, determine the corresponding power factor from the motor 
characteristic curve aiid substitute in Eq. (48). In many cases, 



70 ELECTRIC RAILWAY ENGINEERING 

however, it will be found sufficiently accurate to assume an 
average power factor for the entire curve, with the possible excep- 
tion of the starting value which is usually considerably lower than 
the average operating power factor. 

The area enclosed by a kilowatt time curve is a measure of the 
energy consumed by the car or train during the run; thus, 

^ Area of diagram ,,^. 

^ = 3600 — (*9^ 

„ Area of diagram X 1000 X 5280 ,.„, 

^'= 3600TFS ^^^ 

where 

E = Energy in kilowatt hours. 
El = Energy in watt hours per ton mile. 
W = Weight of car or train in tons. 
S = Length of run from station to station in feet. 

If this energy be expressed in kilowatt hours {E) it will be 
found to be in convenient form for calculating substation de- 
mands, while if expressed in ''watt hours per ton mile" {E-^ it 
will be found useful in comparing various runs with different 
types of equipment and under different service conditions, since 
it has become customary to express the results of power time 
curve calculations for the purpose of simplicity in terms of 
this unit. 



CHAPTER IX 

SPEED DISTANCE, CURRENT AND POWER CURVES 
(CONCRETE EXAMPLES) 

In order that the use of the formulas and the method of plot- 
ting curves outlined in the previous chapters may be thoroughly 
understood, a typical concrete problem will be considered. Al- 
though this particular case has been considered because of its 
rather exceptional changes in grade, involving the most difficult 
phase of the problem, the curves will first be plotted using the 
distances listed in Table VIII, but assuming the track a level 
tangent. Comparative curves will later be calculated and 
plotted to illustrate the effect of grades. 

Table VIII. — Distances and Grades of Typical Run 



Street crossings ' Grade (per cent.) \ ^'''Z"p lleeV^"' 


Distance from 
start (feet) 


A to B 


0.0 
6.0 
5.0 
2.0 
0.5 
1.0 


600 
880 
400 
320 
1240 
760 


600 


B to C 


1480 


C to D 

D to E 


1880 
2200 


E to F 


3440 


F to G 


4200 



A 25 ton interurban car, equipped with four Westinghouse No. 
56, 50 hp., d. c. railway motors and series parallel control, is 
to be operated over this road with a gear ratio of 24-58 at a 
schedule speed of 18 m.p.h. The characteristics of this type of 
motor are found in Fig. 12. 

The initial constant acceleration will be assumed as 1.25 m.p.h. 
p.s., which is a fairly representative figure in electric railway 
practice. 

A force of 100 lb. per ton will be considered as the necessary 
tractive effort to overcome the inertia of both translation and 
rotation in accelerating the car at a rate of 1 m.p.h. p.s. The 
resistance curves found in Fig. 16 are plotted for a car of this 
weight and will therefore be used in this problem. 

71 



72 ELECTRIC RAILWAY ENGINEERING 

The values which must be substituted for the symbols listed in 
Chap. VII, page 59, are therefore as follows: 

p = 125. 

A = 1.25. 

V = 18. 

S = 4200. 
W = 25. 

n = 4. 
Wi = 6.25. 

Using formula (38) the time of run is 

4200 



18 X 1.467 



= 159 sec. 



In order to substitute in formula (36) for gross tractive effort 
the value of train resistance (/) must be approximated. This 
may be done sufficiently accurately by selecting the value from 
Fig. 16 corresponding to the average speed which must be 
assumed for the constant acceleration period. 

Taking this average speed at 10 m.p.h. (/) = 11 lb. per ton. 
From Eq. (38) 

P = (125 + 11) = 136 lb. per ton. 

The gross tractive effort is, therefore: 

T.E. = 6.25 X 136 = 850 lb. (40) 

Referring to the characteristic curves of this motor. Fig. 12, 
the current and speed for this tractive effort are: 

7 = 84 amp. 
V = 20.4 m.p.h. 

The average speed from the start is therefore 10.2 m.p.h. 
which proves the assumption of 10 m.p.h. used in obtaining the 
value of train resistance (/) was sufficiently accurate. Had this 
assumption been much in error a corrected calculation of tractive 
effort should have been made. 

The time required for the period of constant acceleration is 
calculated from formula (41): 

t = y-^p. = 16.3 sec. 
The line {Ob'), Fig. 20, may now be plotted. 



SPEED DISTANCE, CURRENT AND POWER CURVES 73 

The corresponding distance covered is 

s = +-^ X 1.467 X 16.3 = 244 ft. (47) 

This determines one point {n') on the distance curve. 

In order to determine the first point {b'^') on the curved portion 
of the acceleration diagram, an increment of speed must be 
assumed. 

Let dv = b m.p.h. ov v -\- dv = 25.4 m.p.h. 

The gross tractive effort on the characteristic curve corresponding 
to 25.4 m.p.h. is 

T.E. = 400 lb. 

The average speed of this increment being 22.9, the new value 
of train resistance (/') will be found from the resistance curves 
to be 

f = 15 lb. per ton 

The new value of net tractive effort is therefore 



»' = 1*^ - 15 = 49 lb. per ton ■ 


(42) 


The corresponding value of acceleration is 




49 
4' =^25 X 1.25 = 0.49 m.p.h.p.s. 


(43) 


* - A .o - 10.2 sec. 


(44) 



The coordinates of the point (5'') are, therefore: 

(7 4- dv) = 25.4 m.p.h. and {t + dt) = 26.5 sec. 

The corresponding point on the distance curve is found as follows: 

20 4 _l_ o'S 4 
ds = 2 ^ ^-^^^ ^ ^^-^ " ^^^ ^*' ^^'^^ 

s = 244 + 342 = 586 ft. from start. 

Neglecting the grade which is encountered at a distance of 14 
ft. beyond the above point and continuing the above ''step by- 
step" method the values listed in Table IX may be determined 
and the acceleration portion of the diagram plotted to the point 
(^') where the speed becomes constant. 



74 ELECTRIC RAILWAY ENGINEERING 

Table IX. — Calculated Data, Speed, and Distance Time Curves 



dv 


V + dv 


dt 


t + dt 


ds 


s + ds 


5 


25.4 


10.2 


26.5 


342 


586 


3 


28.4 


10.7 


37.2 


421 


1007 


3 


31.4 


22.2 


59.4 


974 


1981 


3 


34.4 


49.1 


108.5 


2370 


4351 



Assuming the total braking resistance including train re- 
sistance h = 150 lb. per ton which, of course, will produce a 
retardation of 1.5 m.p.h.p.s., a straight line may be drawn back 
from r = 159 sec. with the above retardation as its slope. 
Such a Hne is Tr', Fig. 20. 

The train resistance during coasting should be selected as 
nearly as possible to the value which, on the train resistance 
curves (Fig. 16), corresponds to the average speed expected during 
the coasting period. The value of 15 lb. per ton is often taken 
arbitrarily to represent this resistance and will therefore be used 
in this problem. Since this corresponds to a retardation of 0.15 
m.p.h.p.s., a line with this slope is drawn in the position 
ifk), cutting the braking line at point k\ 

If the area of the diagram {Oh'h"fk'T) be measured with the 
planimeter it will be found to contain approximately 123 section 
squares. With the particular scales of speed and time used each 
square is equivalent to a distance of 36.6 ft. The diagram 
therefore represents a distance of 123 X 36.6 ft. = 4500 ft. which 
is greater than the length of the run. The coasting line must 
therefore be redrawn parallel with itself but starting with a lower 
initial speed until, by the ''cut and try" method, the area of 
the diagram is found to correspond to the length of the run 
in feet. Such a diagram is that bounded by the lines {Oh'h"- 
I'm'T), Fig. 20. If the true coasting resistance be now deter- 
mined it will be found to be 13.5. The assumption of 15 was 
therefore conservative. 

The distance time curve will be of value in approximating the 
correct area of the diagram. The values of distance from Table 
IX plotted against time would produce the curve of distance 
covered by the car if it were to be allowed to reach constant speed. 
However, since the power is shut off and coasting begun at a speed 
of 27.5 m.p.h., a new distance curve must be determined beyond 
this point. 



SPEED DISTANCE, CURRENT AND POWER CURVES 75 

The distance corresponding to point (V) is found as follows: 

. ,. 27.5 + 25.4 _ . - 

Avg. T = X = 26.5 m.p.h. 

t = 33 sec. 
ds = 26.5 X 1.467 X (33 - 26.5) = 252 ft. (47) 

s = 586 + 252 = 838 ft. from start. 

Continuing the calculations of distance corresponding to the 
coasting and braking portions of the diagram the distance time 
curve (On' 71"^') is determined which at 159 sec. checks very 
closely the length of the run. 

Speed and Distance Curves for Actual Grades. — If the actual 
grades listed in Table VIII be considered, the curves take 
quite a different and more complex form. Since it was found in 
the previous calculations that the point (})") corresponded to a 
distance but 14 ft. short of (B), Table VIII, where the grade 
changes to 6 per cent, it will introduce little error and simplify 
the calculations considerably to consider the grade beginning at 
this point 

Since the 6 per cent, grade will cause an immediate reduction in 
speed, a decrement of 3 m.p.h. will be assumed. 

dv = Z m.p.h. 7 = 22.4 m.p.h. Avg. V = 23.9 m.p.h. 

(f at 23.9 m.p.h. = 15.4 lb. per ton 

T.E Sit 22.4 m.p.h. = 600 lb. 

p" = 1^ - 15.4 - 120 = - 39.4 lb. (42) 

Retardation = 0.394 m.p.h. p. s. (43) 

* = oil = ''■^ ''''=• 

New point on curve has coordinates as follows: 

V = 22.4 m.p.h. t = 26.5 + 7.6 = 34.1 sec. 

ds = 23.9 X 1.467 X 7.6 = 266 ft. (47) 

s = 586 + 266 = 852 ft. 

The corresponding point on the new distance time curve is there- 
fore determined. 

Following this method, being careful to observe every change 
of grade at its correct distance from the start, the rather irregular 
curve {Oh'h"s"l"m"T), Fig. 25, results. If the distance corre- 
sponding to each of the steps assumed for the speed time curve be 



76 



ELECTRIC RAILWAY ENGINEERING 



calculated, the distance time curve {On'n"'p") may be plotted. If 

ds 
it be remembered that the slope of the distance time curve — 

dt. 

represents speed, the effect of grades in reducing speed will readily 
be detected if the two distance curves are compared. 

While the amounts of coasting in both of the speed time curves 
considered are very generous, the effects of grades both in re- 
ducing the possible coasting and in increasing the coasting 



25 



p. 20 















































SPEED AND DISTANCE CURVES. 










^ 


<^ 


































/ 


^ 


/ 
































, 


/ 


'A 
































^ 


^ 


I 


V 






































V 








r' 




















/ 










4- 








\ 


















--? 


1 




""^ 






'^ 


v" 










\ 
\ 
\ 














• 


n 


1 

SI 




\^ 


k; 




/■ 


\ 


\ 








\ 














■V 


1 
1 


1^ 


^^ 


s"_ 


V 






\, 


\ 






















1 


1 
1 


1 

1 




/ 


V 




\ 


\ 


K 








\ 














/j 


1 

1 


1 
1 




// 


/ 








\. 


<^ 


\. 




\ 
\ 














/i 


1 
1 


1 
1 


/ 


/■ 


^v. 


^ 








\^ 


F^ 






\ 










/ 




1 
1 


1 


V 






■V 


^•^^ 










X 


s 


W^ 










/ 




1 

1 


/ 












^v 


-•. 






\ 
\ 


\ 


^m 


^t 


^k 






/ 


1 


^ 


















^v. 


^ 




'n 












/ 


4 


/i 

1 


\ 
1 

1 


















" 


^^ 


\ 


1 


n" 








/ 


4 


9\ 


^' 












q- 










">v^ 


^-^4 


T 









4000 



JOOO 



1500 



1000 



500 



10 20 



70 80 

Time in Seconds 

Fig. 25. 



retardation in the second case are marked. If stops were neces- 
sary in this distance the coasting periods would be greatly 
shortened and possibly eliminated if the same schedule speed 
were maintained. 

Current and Power Curves. — The gross tractive effort during 
the constant acceleration period {Oa'), Fig. 25, was found to be 
850 lb. which required a current value per motor of 84 amp. 
During the first half of this same period plotted to the same scale 
on Fig. 22, therefore, the current per pair of motors in a four motor 



SPEED DISTANCE, CURRENT AND POWER CURVES 77 

equipment is 84 amp. while the current per ear is 168 amp. 
In the second or parallel half of the period, however, the corre- 
sponding values of current are 168 and 336 amp. respectively. 
In determining the other points on the current curve such as the 
current after 20 seconds have elapsed, for example, it is found 
from Fig. 25 that the speed is 22.5 m.p.h. Referring to the speed 
characteristic, Fig. 13, the corresponding current is found to be 64 
amp. per motor or 2 6 amp. per car since all four motors are 
now operating in parallel. This value is plotted against a time 
abscissa of 20 sec. on Fig. 22. Following out this method the 
current required for operating the car over the level track will be 
represented by curve {00"fkh"lq'), Fig. 22, while the corre- 
sponding current with the actual grades introduced is illustrated 
in curve {00"fkh"mnq"). 

As an average voltage of 500 volts has been assumed on this 
road the ordinates of the two similar curves of Fig. 23 are 500 
times those of Fig. 22 reduced to the convenient scale of kilowatts. 
If these curves be compared with the speed time curve. Fig. 25, 
the increased values of power required as the car enters the grades 
will be noted. 

The areas of the two kilowatt time diagrams. Fig. 23, are 3960 
and 12,100 kw. sec. respectively. Applying formula (49) the 
energy required by the level run is, 

^ = IS = 1.1 kw. hr. (49) 

while that of a run involving the existing grades is, 

E = ^~ = 3.36 kw. hr. (49) 

The energy consumptions for the two runs expressed in watt 
hours per ton mile are, 

^ 3960 X 1000 X 5280 .. _ . .^ .. .^^. 

^' = 3600 X 25 X 4200 = ^^'^ '''' ^^'/^^^ ^^^^ ^^^^ 

^, 12100 X 1000 X 5280 _^ , . .. .^^, 

^ ' = 3600 X 25 X 4200 = ^^^ '''' ^''/^^^ ^^^" ^^^^ 

Since the rolling stock and equipment in this case are rather 
lighter than that of average interurban practice, the value of 55.3 
watt hours per ton mile for the level track is rather a low figure 
while the steep grades in the latter case render the figure 169 for 
E'l rather above the average. The very fact, however, that these 



78 



ELECTRIC RAILWAY ENGINEERING 



c >■ 




















o 1 




A.^o7 






?oS 


Q ^ 






CM O --I 




t^ 




- • Tt< TtH CD (M IC 


d 


^ o ,, 




P-l .OiOOOOOiOfN 


Q (M (M CSl t> 


t; oj-^ 


(N 


1^1 


.• ^ Tfi CD CO lO 

PM .O'oooooooio 


H 


Q (M (N CM t^ 






CO 


j>^ 


-^ 


• CD CD rJH 1> CD 


i^ 


J 


f^ .OocDOiMi-HOO 


^ ^ ^ ^ 


-^^ 






OJ 


(M 






• CD 05 (N CD <M 

Ph .Uocmocdcdoo 


h5 3 


H 


p j.^ c. ^ 




<M CD 


>IWffiP^ 


• 00 lO Oi O 05 

pt, .t^OOCDOiOO^ 


^^=srt 


^ ^ ^ 1 CO 0. 




■—I 




05 03 




d ^SaScD 




=8 • 


fL, H^] • .... 




Q Tj< 1> O CO O t- 


CT> 03 




^« 


Q |^°^°§^ 






CO 00 




lO TJH 


Wp^ 


^O^ CDOOOO 


^ . yA . . . . . 


^ CO O O OS o o 
^ 05 (M 1 rt< CO 




CO 00 




- O CD o I> o o 


^=^ 


Ah i-q ..... 

J l> O O Tt< o »o 
^ t> (N 1 tH CO 






05 




^- <M »0 




P S ?5 =P ^ ° § 


Ol 


^w 


O O5.-H(N00CD 


r^ CD CO O CO O >-< 
W CD (M _j_ (N 00 






CO 




ic 00 


W'rt 


. O CD O i-H CD (N 


^ . t-q 


J lO O O (M O ^ 


^tf 


CO 


>^w 


d, CDOrnSTt* 


^■^ 


^J^CDodoJcJiO 
^'^ "-H (N _|_ CM 00 


















OJ 














cl 
















s-^ 


■g 








ai „ 


S r a 


C3 








ggl as 


o 






C 


"ill'll! 






Q .S •?l'«^ M « ^ ^ 1 














c^ 


<5 


C 




^ 


•< CO cc 


^ I 



a; -^ 






fl o 
o >• 



£ § .s 

£ g rt 

^ O " 

"fl o o 

g -» M 



2i W 



CO -|J ^1 

iJ "^ s 

■'^ <D O 

I. .5 ^ 

o o H 



SPEED DISTANCE, CURRENT AND POWER CURVES 79 

values of energy vary over so wide a range illustrates the marked 
effects which may be attributed to local conditions and em- 
phasizes the necessity of a complete and detailed study of each 
proposed road before accurate estimates can be made of its cost 
of construction or dependable conclusions drawn regarding the 
advisability of its installation. 

In Table X will be found results of actual tests upon cars and 
locomotive propelled trains for various types of service. 



CHAPTER X 
SPEED TIME CURVES (STRAIGHT LINE) 

The method of plotting speed time curves outhned in the 
previous chapter is most desirable for final calculations where 
considerable accuracy is necessary. For preliminary approxi- 
mate results, however, it is not necessary to go to this refinement 
and the so-called '' straight line" speed time curve described below 
is therefore used. 

In Fig. 26 will be found reproduced the speed time curve 















1 




























COMPARISON OF SPEED - TIME CURVES 








30 








































f. 


b 




























25 






-l^ 


/^ 


ks 






























; 






% 


k 






















W 20 
§3 




a/ 

T 












U 


S^ 


















r*^ 


S,^ 










^ 


H. 
















Il5 






1 


s 


\. 












% 


N 
















1 






^ 


v 












%l 


»s. 








10 


1 




1 
1 










\. 


s 










^ 


V 


c 




/ 




1 
1 














\ 












V 




5 


/ 




1 


















e" 












/ 




1 


















\ 














1 




If 
















\.' 










d 



20 



40 



GO 



80 100 

Seconds 
Fig. 26. 



120 140 



160 



(oahcd) calculated in Chap. IX for a straight level track, Fig. 
20. If, now, the time (Od) and the distance, represented by the 
area (Oahcd), are kept constant and the acceleration be assumed 
constant, i.e., the acceleration portion of the figure a straight 
line, the diagram {Oaec'd) may be drawn with the same area and 
with the average assumed coasting and braking retardations of 
0.15 m.p.h.p.s. and 1.5 m.p.h.p.s. respectively. Such a chart, 
although it may vary considerably in some details from the more 

80 



SPEED TIME CURVES 



81 



accuratel}^ drawn curve previously considered, is extensively used 
for rapid calculations of possible schedules for a given road and 
for the rough determinations of required equipment and pre- 
liminary estimates. 

Granted that the straight line diagram is sufficiently accurate 
for most practical purposes, an unlimited number of similar speed 
time diagrams may be plotted for the same distance and time by 
varying the rate of acceleration but with constant coasting and 
braking retardations. Such a series of diagrams for a 1 mile 
run in 120 sec. appears in Fig. 27,^ in which (OBC) represents 
a run with no coasting and therefore the lowest possible rate of 
acceleration, while the other extreme case, which is of course 
theoretical only, is represented with an acceleration (OA) in- 



h ^0 

O 



















i^# 










.^A i 




























.ri<»- 






,. 


." 


y" 


^T 


\i 














, 


.:. -L\^_ 




:^^i-T" 


y 




1 


\ 












A L5.^=5^=,Si:] 


yd^i — \ — '~y^^-^^ 


1 




\ 












^^^^^nr-U^T^ 


■ — — . 


rA 










I//// IX 




~7^~i"^^^~^^^ 


^^^ 


^-~^^^:::r^^ 


^ 








}/ /i / y 


/ 




y 








• 1 1 \ — r^-^^^^^ 










/ 


' 


^ 


/ 






























\ 






/// 


^ 


^ 
































\ 






///^y 






































\ 




wy 








































k 


V^^r 




... 






























lc\| 



20 40 60 80 100 120 

Seconds 

Fig. 27. — Typical speed time ounces. (Varying rates of acceleration.) 

finitely great. Between these two limiting values there are a 
number of possible selections to be made, the gross tractive efforts 
listed on the chart including the net effort necessary for accelera- 
tion plus the 15 lb. per ton train resistance assumed for all dia- 
grams. It should be noted that the dotted line (A5) is the locus 
of maximum speeds for all diagrams. 

Furthermore, if the distance still remain constant at 1 mile and 
the time for the entire run be varied the more complete chart, 
Fig. 28,^ results, which is made up of a series of charts like Fig. 27, 
each having its own acceleration variations for a fixed distance 
and time. The dotted curve of Fig. 28 represents the locus of 
maximum speeds necessary to cover the distance of 1 mile 
in any given time represented as an abscissa. For example, 

1 Taken from "Electric Traction," by A. H. Armstrong. 



82 



ELECTRIC RAILWAY ENGINEERING 



if it be desired to cover the mile run in 150 sec, the braking line 
terminating at 150 sec. shows the maximum speed with any 
acceleration to be 48 m.p.h. corresponding to a gross tractive 
effort of 51.2 lb. per ton. If other rates of acceleration are pos- 
sible the particular chart designated by the point 51.2 may be 
treated as outlined in Fig. 27. 

These charts are of little use, however, unless readily applicable 
to various lengths of run. Such application may be made in the 
following manner. 

It can be readily proved geometrically that the ratio of the alti- 
tudes or bases of two similar trapezoids is that of the square root 



UU 1 


^? 


.Lb.] 


fS 


^ 


on 


■^ 


•OS 


r 














"^ 
























r 




















































V^ijw 




















































V/VNtS''' 


















































n 


\/ 


Y^ 




"> 












































15 


'\\ 


y 




A^ 


















































'A 




/\ 


'^5^ 


^ 










































j A 


X 


\/j 


\ 




\^N 


^ 




H 






































JZ/ 


\'V 




y 




V 


^ 


v^S*' 


N 




































Ivi 


\V 


y" \ 


A 




'K 


V 


^-f 


































Xi 


X 


\Jc- 




L'^ 


/ 


\-X 


y "y 
































'uxL 


i\ 




•V-; 


K 


V' 


V, 


^ 








\- 


-^ 


-#* 




V 






















=fe^ 


% 




1 




^ 


F 


q 


—A 


^ 




A 






^ 


^ 




> 


f 


:i 
















e^C3 




c>' 


' 








^- 




ivG 


1? 


'-A 




Vq 


K 


jp= 






Lt. 


-^ 






\c= 


rinr 


^'- 


^ 








-- 


~-. 


_. 


f 




ijjr/ 


/ ^ 


// 


n 




^ 


^ 


\ 


'V 






\ 






i 


=— ■ 


=\- 


— 




— 




-:^ 


=^ 






If// A 


/// 


y. 


\ 




H 


i 


$ 








P^ 






' 




^ 
















\ 




1/ 


\w^ 


^ 




^ 




^^ 








\ 




\ 




y 








\ 


]li 


mS'^ 


^ 


"^ 


^ 




v\ 


\ 


X 






\ 


\ 






--> 






\ 




\ 




\ 








\ 


I 


'^^ 


^ 








\ 


_\ 


_\ 






J 


J 










., 


^ 




\ 




\ 








\ 



120 
Seconds 



180 



240 



Fig. 28. — General speed time curves. 



of their areas. The speed time diagrams which have been con- 
sidered in this chapter are trapezoids with altitudes representing 
maximum speeds, bases representing time, and therefore with 
areas expressed in terms of distance. If the length of run be 
changed, keeping the same acceleration and coasting and braking 
retardations, the diagrams for the two lengths of run will remain 
similar and the following formulas may be derived for the calcula- 
tion of maximum speed and time. 

T = Schedule time for original run. 
T' = Schedule time for new run. 
S = Distance of original run. 



SPEED TIME CURVES 83 



S' = Distance of new run. 
Vm = Maximum speed of original run 
V'm = Maximum speed of new run. 



F'„ IS' 



F„ ^S ^''^ 

As an illustration of the use of these formulas, it will be as- 
sumed that the speed time diagram is desired for a run one-half 
the length of that considered in the previous chapter (2100 ft.), 
Fig. 26, with the same rate of acceleration, coasting, and braking. 
From the diagram the following values may be scaled : 

T = {Od) = 159 sec. 
Vm = (ef) = 28.5 m.p.h. 
S = 4200 ft. 

Substituting in Eqs. (51) and (52), 

r = 159\/0T5_= 112.4 sec. (51) 

V'm = 28.5\/0.5 = 20.1 m.p.h. (52) 

Plotting these values, the diagram {Oe'd'S!) results and there- 
fore represents fairly accurately a speed time curve for a distance 
of 2100 ft. with a minimum of labor involved in its determination. 

Energy Calculations. — As the acceleration was assumed con- 
stant in the above diagrams, it is usually not sufficiently accurate 
to derive from them the current and kilowatt time curves as was 
done in Chaps. VIII and IX. The energy required for the run 
may be closely approximated, however, by the following method, 
which may also be used to advantage as a check on the power 
time curves when the latter are plotted by the ''step by step" 
method. 

Assume the following nomenclature: 

Y = Average speed in m.p.h. 
Vc = Initial coasting speed in m.p.h. 
Vb = Initial braking speed in m.p.h. 

r = Total train resistance in lb. per ton including 

if±g + c). 

El = Energy in watt hours per ton mile. 

,, , 2000 IF 

m = Mass of car = — 

9 



84 ELECTRIC RAILWAY ENGINEERING 

h = Braking force at periphery of car wheel in lb. per ton. 
Sc = Distance traveled from beginning of coasting period 

to stop with no braking. 
Sb = Distance traveled from beginning of braking period 
to stop. 
tc = Time of coasting in seconds. 
tb = Time of braking in seconds. 

7 X 5280 X r X 746 ^ ^^ ,^^, 

^^ = 60X330007 = 1-^^^ (^^) 

This may be considered with little error to be (2r). 

This represents in simple form the net energy at the wheels of 
the car. To obtain the gross input to motors this must be divided 
by the efficiency of the motors with gears included. 

Energy During the Braking Period. — Furthermore, it should 
be noted that neither Eq. (53) nor the formulas of Chap. VIII 
includes the power required to stop the car. To determine this 
power exerted during the braking period, proceed as follows : 

m{Vb X 1.467)^ .... 

e = 2 " ^^^^ 

but 

e = Sbih -\-r)W (55) 
therefore 

we.7._L_ ^ 200017(1.4677,)^ . 

WSbih + r) = 2g " ^^^^ 

The power during the braking period is therefore 

_ Ft. lb. per minute ^ mWSbjh + r) 
P* ~ 33000 33000^6 

or simplified 

60 X 2000T7(1.4677,)2 WV% 

HP- = -32.2X2X33000^5 = ^'^^^ "IT ^^^^ 

Coasting Energy and Train Resistance. — If, however, the 

above reasoning be apphed to the results of a coasting test in 

which the car or train is allowed to coast to a standstill from 

various initial speeds the train resistance may be calculated thus: 

^.^ 2000 17(1.467 7c)2 ,,.. 

whence 

r = 66.8 ^ (59) 



SPEED TIME CURVES 85 

If, however, the portion of the coasting line to the point where 
brakes are appUed is being considered, formula (59) becomes 

Y 2 _ T- 2 

r = 66.8 -^-^ — - (60) 

By thus combining the straight line speed time charts with the 
calculation of energy from the above formulas, a rapid although 
approximate method of calculating train performance is provided 
which will be found of great convenience. 



PART II 

POWER GENERATION AND 
DISTRIBUTION 



CHAPTER XI 
LOCOMOTIVE TRAIN HAULAGE 

In the previous chapters, the problems that apply particularly 
to motor car train haulage have been studied. This chapter 
will be devoted to a study of the application of electric loco- 
motives as a source of motive power for railway trains. 

Drawbar Pull. — The drawbar pull of a locomotive is the 
force exerted by the locomotive on its drawbar. The more im- 
portant of the factors on which this force depends are as follows : 

1. Characteristics and capacity of the motors. 

2. Gear ratio. 

3. Diameter of drivers. 

4. Train resistance of the locomotive. 

5. Adhesive weight. 

6. Coefficient of adhesion. 

The characteristics of a 100 ton, direct current, freight loco- 
motive are shown in Fig. 29. The points marked C and " 1 
Hr." indicate respectively the continuous and 1 hour ratings of 
the locomotive. It will be noted that tractive effort has been 
used for the abscissa of these curves instead of amperes, as 
in Fig. 13; the arrangement here used is believed to be more 
convenient for use in the solution of locomotive train haulage 
problems. 

The effect of changing the gear ratio of the motors has been 
discussed in Chap. V, and therefore needs no further discussion 
here. 

For a given motor speed, any increase in the diameter of the 
drive wheels of a locomotive causes a proportional decrease 
in the tractive effort, and therefore a decrease in the drawbar 
pull. Considerations such as stresses at contact area between 
driver and rail, tire wear, surface speed of journals, and track 
maintenance fix the minimum driver diameter for a given weight 
on driver axle. 

As has been intimated in a previous chapter, it is a very 
difficult matter to secure consistent results in experimental deter- 

89 



90 



ELECTRIC RAILWAY ENGINEERING 



minations of train resistance. Authentic data on the subject of 
locomotive train resistance are scarce. The practice of engi- 
neers differs widely. Burch recommends that 22.2 lb. per ton 
on drivers be used for the frictional resistances and 0.24F2 
for the total air resistance of the locomotive. ^ Some engineers 
use a constant value of 15 lb. per ton for all conditions of track, 
weather and speed. Formula (24) has for its basis the tests 
made on the New York Central electric locomotive No. 6000 



35 



2400 30 



I 2000 25 



gl600 20 
'2 1200 '^ 15 



i 800 



400 



10 





Locomotive Characteristics 
100 Tons Total Weight 
4 No. Motors 
4 No. Driving Axles 
600 Voltage 
79/23 Gear Ratio 
48 Inches, Driver Diameter > 
Motors In Parallel / 


/ 


700 
600 
500 

400 




/ 










/ 




V 




1 Hr. y 


'f 


,*^ 


iy^ 


\ 




.^C^nr. 


y£^ 

^ 


^ 




300 
200 
100 




/, 


/ 




—Speed 


-~- 


// 


/ 






§ 

1 

A 




// 








< 





10 20 30 40 50 60 

Locomotive Tractive Effort, Thousands of Lb. 

Fig. 29. 



during its 50,000 mile endurance run. The locomotive resistance 
may be calculated from a modification of formula (24) 

50 0.00272a 

(61) 



h 



+ 0.03 Y + 



where /i = Frictional and air resistances of the locomotive in 
lb. per ton. 
Y = Speed in m.p.h. 
W\ — Weight of the locomotive in tons. 
a = Cross section of locomotive above the axle in sq. ft. 

^ Burch's "Electric Traction for Railway Trains." 



LOCOMOTIVE TRAIN HAULAGE 



91 



This formula* gives results which check very well with those 
secured in the New York Central tests with the locomotive 
running alone. ^ The curve in Fig. 30, giving the train resistance 
for the 100 ton freight locomotive whose characteristics are 
shown in Fig. 29, was plotted from this formula. 

The adhesive weight of a locomotive is defined by the American 
Institute of Electrical Engineers as ''The sum of the weights on 
drivers and of the drivers themselves. "^ The ratio of the ad- 
hesive weight to the total weight of the locomotive varies from 



10 



c5 



















El 


ectric Locomotive Trai 


n Resistam 

— 0-4-4-0 


;e 








Wheel Arrangement 
















^^ 


■^ 



















































10 15 20 25 

Speed in.M.P.H. 

Fig. 30. 



30 



35 



40 



about 0.65 for large high speed passenger locomotives to 1.00 for 
freight and interurban locomotives. Interurban locomotive 
weights vary between the limits of 25 and 75 tons, 50 tons being 
an average weight. In heavy traction service such as obtains 
on electrified steam lines, the locomotive unit weights vary 
from 75 to 150 tons. A unit weighing about 100 tons seems to 
fit present requirements best. 

The coefficient of adhesion is -the ratio between the maximum 
tractive effort that can be exerted without slipping the drivers 

1 See also "Standard Handbook for Electrical Engineers." 

2 Proceedings A. I. E. E., Aug., 1914. 



92 ELECTRIC RAILWAY ENGINEERING 

and the adhesive weight. Electric locomotives are often rated 
at 25 per cent, adhesion; that is, the tractive effort which the 
motors can develop momentarily is 25 per cent, of the adhesive 
weight. In Fig. 29 the dashed ordinate indicates the 25 per 
cent, limit. When track conditions are bad, the maximum 
drawbar pull which a locomotive can exert is lowered because 
of the low coefficient of adhesion. 

Table XI. — Coefficient of Adhesion^ 

Per cent. Per cent. 

Most favorable condition 35 when sanded 40 

Clean dry rail 28 when sanded 30 

Thoroughly wet rail 18 when sanded 24 

Greasy moist rail 15 when sanded 25 

Sleet covered rail. 15 when sanded 20 

Dry snow covered rail 11 when sanded 15 

For a given speed, if 

T.E. = Tractive effort of all motors on the locomotive. 
D.B.P. = Drawbar pull of locomotive in lb. 
g = Grade resistance in lb. per ton. 
c = Curve resistance in lb. per ton. 

ri = (/i ± sr + c) 

the drawbar pull, 

D.B'.P. = T.E. - W,{fi ±g + c) (62) 

= T.E. - WiVi 

Power Required for Train Haulage. — The power required for 
train haulage may now be calculated. 

Let U = Energy, in watt hours, required to haul trailing load 1 
mile (measured at drawbar). 
Ut = Energy, in watt hours, required to haul entire train 1 

mile. 
W = Weight of trailing load in tons 
r = {f ± g -\- c) ioY trailing load. 
P = Power input required for the train, as measured at the 

drawbar, in kw. 
Pt = Total power input to locomotive in kw. 
7) = Average efficiency from current collector to drive 
wheels. 

1 Burch's "Electric Traction for Railway Trains." 



LOCOMOTIVE TRAIN HAULAGE . 93 

From formula (53) 

U = 1.99rW 
Therefore, 

^ ^77 ^ L99rW 

1000 1000 ^ ^ 

The horse power exerted at the drawbar will be 
lOOOF l.mrWV D.B.P. X V 



746 746 375 



(64) 



If T.E. is substituted for D.B.P. in formula (64), the formula 
may be used to calculate the ''horse power at rim of drivers," 
or the brake horse power of the locomotive. The total energy 
input required to haul the train 1 mile will be equal to the 
energy required to haul both cars and locomotive, divided by 
the efficiency of the locomotive, or 

_ 1 .99rTF+ l.QQriTTi 1.99(rTF + riTFQ 
Ut — — 

The power input to the locomotive, 

IMVjrW + nW,) 

^' = looo^o^ (^^-^^ 

For ordinary calculations (2r) can be used instead of (1.99r), 
in the preceding formulas, and t] may be taken as 0.80. These 
formulas are based on the assumptions of constant speed and 
constant total train resistance, and therefore do not take into 
account the variable speed and train resistance conditions which 
obtain in practice. The average power input and the average 
energy input per train mile for a given run calculated by using in 
these formulas the average speed and average total train re- 
sistance will be only approximate. However, because of their 
convenience the formulas are much used by engineers in making 
preliminary estimates and checking calculations. Where more 
accurate results are desired the power time curve method, 
explained in Chap. VIII, may be used. 

Determination of the Tonnage Rating of a Locomotive. — In 
order to assist the train crews and yardmasters in making up 
trains, and to prevent overloading of locomotives, railroad com- 
panies usually supply their operating men with a table of tonnage 
ratings which gives for each locomotive the number of trailing 
tons it can haul over the division of the road on which it is 



94 ELECTRIC RAILWAY ENGINEERING 

operated. The calculation of locomotive tonnage ratings is 
one of the common problems in train haulage. A solution of 
this problem can be best illustrated with an example. 

It is desired to determine the tonnage rating of the locomotive 
whose characteristics are given in Fig. 29 for a section of road 
which has the following track conditions for a given direction 
of traffic : 

Average grade 0.2 per cent. 

Ruling grade 1.1 per cent. 

Length of track section 10 miles. 

The ruling grade which is located at the beginning of the 
section is 2350 ft. in length, and the first 926 ft. of it is on a 3 deg. 
curve. 

The average empty freight car weighs about 15 tons and 
the average loaded car on this road weighs about 60 tons. It is 
desired to calculate: 

1. The number of loaded cars the locomotive can start on the 
ruling grade. 

2. The number of empty cars the locomotive can start on the 
ruling grade. 

3. The number of loaded cars the locomotive can haul at rated 
speed over the section. 

4. The number of empty cars the locomotive can haul at 
rated speed over the section. 

A solution of the problem, taking up its parts in the order 
above enumerated, follows: 

1. The maximum tractive effort which the locomotive can 
momentarily exert, Fig. 29, is 50,000 lb. The train resistance 
of the locomotive at starting. Fig. 30, is 5.25 lb. per ton. 

Experience has shown that, in order that a train may be started 
and brought up to speed under all ordinary track conditions, an 
accelerating force of about 15 lb. per ton of train weight must be 
allowed. The tractive force required by the locomotive at 
starting, is 

100(15 + 5.25 + 1.1 X 20 + 3 X 0.6) = 4400 lb. 

(The curve resistance is here estimated at 0.6 per ton per degree 

of curve.) 

The starting drawbar pull is, therefore, 

50,000 - 4400 = 45,600 lb. 



LOCOMOTIVE TRAIN HAULAGE 



95 



The train resistance (/) of a 60 ton freight car at starting (as- 
sumed to be equal to the resistance at 5 m.p.h.) is, Fig. 31/ 
3.25 lb. per ton. The total train resistance (r) of one car for 
the given track conditions is 

3.25 + 1.1 X 20 + 3 X 0.6 = 27.05 lb. per ton. 



12 

f 
1 

c 
.2 ^ 

B 
2 A 














^^ 


^ 












^ 




^ 










^^ 


^ 




^ 




^ 








^ 




^ 




^ 








^ 




^ 


2 




^S 































10 



30 



15 20 25 

Speed in M.P.H, 

Fig. 31. — Freight car train resistance curves 



35 



The tractive force required at starting is 

27.05 + 15 = 42.05 lb. per ton. 



45600 



15 



20 ^ 



40 



= 1085 = number of tons the locomotive can start 



42.05 
on the ruling grade. 

— ^7— = 18 (approximately) = number of cars. 

2. Proceeding in a similar manner, the empty car tonnage 
and the number of empty cars will be found to be respectively 
985 tons and 65 cars. 

^ From Bulletin No. 43, Engineering Experiment Station, University of 
Illin ois. 



96 ELECTRIC RAILWAY ENGINEERING 

3. From Fig. 29 the continuous tractive effort of the locomotive 
is found to be 15,000 lb. and the corresponding speed, 17.4 m.p.h. 
The tractive force necessary to haul the locomotive at 17.4 
m.p.h. is 

Wiifi + g) = 100(6.25 + Ko X 20) 
= 1,025 lb. 
The drawbar pull, 

D.B.P. = 15,000 - 1025 = 13,975 lb. 

The tractive force necessary to haul 1 ton of the trailing load is 

r = f -\- g = 3.9 + Ho X 20 = 7.9 lb. 

„ Q = 1769 = number tons trailing load. 

-^^ = 29 (approximately) = number of cars, 

4. In a similar manner the number of trailing tons of empty 
cars will be found to be 1065 and the number of empty cars 71. 

Under adverse rail conditions the coefficient of adhesion 
would be less than 25 per cent, and the values obtained in (1) 
and (2) would have to be decreased proportionately. 

It is evident from the above results that the loaded car tonnage 
rating of this locomotive for the given section of track is seri- 
ously limited by the ruling grade. Also, it is interesting to note 
that this locomotive can start on the ruling grade nearly as 
many empty cars as it can haul continuously at 17.4 m.p.h. 

Since the motor current during the accelerating period is far 
above the continuous current rating of the motors, it is usually 
necessary to check the motor heating for the run over a given 
section. A method of checking the motor heating will be 
explained under the heading of Speed, Distance, Current, and 
Power Time Curves. 

Determination of the Locomotive Capacity Required for a 
Given Train. — This problem is the reverse of the preceding one, 
and while ordinarily not as common, uncjer present conditions of 
heavy electric traction where electric locomotives are re- 
quired to haul over certain sections of road trains that are 
hauled over other sections by steam locomotives, it is a problem 
that the railway engineer is often called upon to solve. 

With track and train conditions known, the drawbar pull and 
drawbar horse power necessary to haul the train over the road 



LOCOMOTIVE TRAIN HAULAGE 97 

can be readily computed by methods previously explained. The 
problem, then, is to find a locomotive which can develop the 
required drawbar pull at the required speed. The usual solu- 
tion is a '' cut and try " method. A locomotive which can develop 
the necessary drawbar horse power (due allowance being made 
for excessive motor heating during accelerating periods) is se- 
lected and its gear ratio, or gear ratio and drive wheel diameters, 
changed until a combination is found which will allow the loco- 
motive to exert the required drawbar pull at the required speed. 
Speed, Distance, Current, and Power Time Curves. — In the 
solution of problems connected with locomotive train haulage, 
speed time curves are used: 

1. To determine whether or not a given locomotive hauling a 
given train can maintain a certain schedule speed. 

2. To determine the running time required by a given loco- 
motive to haul .a given train over a given section of track. 

3. To aid in the accurate determination of current time and 
power time curves and motor heating. 

Since the runs of locomotive hauled trains are usually much 
longer than those of motor car hauled trains, the time required 
for accelerating and braking is usually small as compared with 
the total time required to make the run. The '' straight line" 
speed time curve, therefore, may be used with a very fair degree 
of accuracy in determinations (1) and (2), the constant speed, or 
*' balancing speed" as it is often called, part of the curve being 
plotted for the speed at which the train resistance of the trailing 
load just balances the drawbar pull of the locomotive. 

Determinations of the current and power time curves and 
motor heating require the use of the ''cut and try" method 
of calculating the speed time curves. 

The heating of a series motor is proportional to the square 
of the current (copper losses only considered). The h ating 
effect, then, for the time (dt) and current (7) will be proportional 
to Pdt. If these heating effect increments be integrated over 
the time (t) necessary to make a complete run and the summation 
be divided by the time (t) , the quotient will represent the square 
of a steady current which flowing for the time (t) would produce 
the same heating effect as was produced by the variable current 
that actually existed in the motor windings. As the continuous 
current rating of a motor for a given operating voltage can 
always be "readily determined by test or secured from manu- 

7 



98 ELECTRIC RAILWAY ENGINEERING 

facturers' data, the root-mean-square current offers a con- 
venient method of checking the motor heating of direct current 
series motors. 

Concrete Example of Speed, Distance Current, and Power 
Time Curves and Motor Heating Calculations. — ^^Given the fol- 
lowing data: 

100 ton, 600 volt locomotive. Fig. 29. 

Trailing load of eighteen 60 ton cars or 1080 trailing tons. 

Track conditions and data as in paragraph on determination 
of tonnage rating. 

Locomotive train resistance as in Fig. 30. 

Car train resistance as in Fig. 31. 

Braking rate 0.75 m.p.h.p.s. 

Required to determine: 

1. Time necessary to make the run. 

2. Average running speed. 

3. The suitability of the locomotive from the standpoint of 
motor heating. 

4. The energy input, in kw. hr., required to make the run. 

A force of 100 lb. per ton will be considered as necessary to 
accelerate the train 1 m.p.h.p.s. 

Let it be assumed that the motor connections during the 
''notching up" period are (1) all motors in series, (2) motors in 
series parallel, (3) all motors in parallel, and that the ''notching 
up" time is equally divided among the three periods. It will 
also be assumed that the motor current is kept constant at 
600 amp. during the "notching up" period. 

In dealing with locomotive hauled trains it is more convenient 
to make this last assumption than to assume some definite rate 
of acceleration as was done in Chap. IX. Since those locomotives 
which are equipped with automatic controllers automatically 
keep the motor current constant during the notching up period, 
and the ammeter equipment on locomotives not so equipped 
enables the engineman to keep the current constant during this 
period, the preceding assumption accords well with operating 
practice. It is also more convenient to use the tractive effort 
of the locomotive rather than that of a single motor in the speed 
time curve calculations. Otherwise the method of calculating 
the various curves is the same as was explained in Chaps. VII 
and IX. Since the method was discussed in detail in Chap. IX, 
it has not been thought necessary to repeat the details of the cal- 



LOCOMOTIVE TRAIN HAULAGE 



99 



1 

o 

c 


si 


i-iiNot^.-iioroco 






c 

I 




^1 


OOO(M0000(N00 








|!l 


O" CO* (N" tjT (m' oT 




i 


+ 


O O •* TjH 'if 00 o 
i-T <N CO "f t^ (N (N 






■S 


O O ■* O O -* (M 
05 C<1 (N l> (M O t^ 

O CO CO iC 1> 1-1 CO 

-' ^ "^ ^ i 


of 


+ 


lo lo 03 a> •^ Tf< •* 








(M t^ Tf Tt< l> (N OC 

;^ ^ S g 5§ ^. ^ 


^ 


(N lO l> O <N lO CO 
rH O (N O O t^ (N 


i 

05_ 


^ 


i> o 1^0 o 00 o ^7; 
^ (N r^ (N o o ^ 
^ o o o O o «> 

d 6 6 6 6 6^ 








O O O O lO o o 
O O CC O <N O O 
00 ■* «0_ CO o> o o 

CO csT oo" cvT o d" 






Total 
train 
resist- 
ance 


o o o o Jn o o 

O O t> O t^ lO o 

TJH_ 0_ CO lO CO t- O 

(N O 05 of cT oi" 








O Co" oo' rn" O oT 

Tt< CO >— 1 1— 1 1-H 








OOO<N0000CM§O 
CO(NTt<X'-i0000I>O 

r-T <m" ,4 rs" 








O lO >0 O lO lO o 
O lO CT> (M O 05 O 
O ^ C^I IN (N 1-1 O 






+ s 

t-^ 


(N iC »0 >0 O »0 

CO "^ O 00 O O 








-§ 


(M CO O O lO 

CO iH (N -ra o 














:5 : o 
: "3 —■ o 

= .3 S .S .2 s I 
a 2 g 2 2 a .2 

ill! |i 1 


c 

1 

c 
'St 

I. 




"c 









fl 
















0) 




























(h 














:3 














o 














CI) 




























03 














1 




+3 










cr 














^' 




Ttf 










pi 




o 










c3 




rH 










a; 




lO 










d 




^ 










^ 




II 






















o 




^ ^ 










?-l 




(M 










II 




1^ 












CO 










to 


d 


+ 


5J 








II 


2 

n 


^ 

^ 


to 








rt^ 






lO 










Tl 


1 


rH 








CO 


(D 




11 




1 




T—< 




'^i^ 

o 


CO 
1—1 




o 


&x 




o 

rH 


lO 


X 

to 




II 


?r 


g 


II 




o:> 




1 


2 


CO 

T— 1 


00 


i 


s 


1 

to 


TtH 


II 


o 


II 


Ti 


••^3 




»o 










fli 


o 


CO 


o 






'^ 


> 

03 






^ 


Q 


01 


OJ 




II 






CO 


a 


a 


o 


8 


II 

CO 


1 

:3 


CO 

§ 




bC 


1 


Tt^ 


^^•^ 


s 


§ 


3 


r-( 


o 

o 






03 

1 


p 


5 


6 



100 ELECTRIC RAILWAY ENGINEERING 

culations here. Table XII gives the results of the calculation 
and illustrates a convenient form of record for such calculations. 
If more accurate results are desired, average values of 7, T.E., 
and R may be used in the calculations. 

It will be noted that the first and second total distance values 
do not quite correspond with the ends of the curve and 1.1 per 
cent, grade respectively, but the error resulting from the assump- 
tion that they do so correspond is negligible. The braking time 
and distance were calculated from the known speed at the begin- 
ning of retardation and the rate of retardation. 

The root-mean-square current as calculated is 251 amp. per 
motor, while the rated continuous current of the locomotive, 
Fig. 29, is 262 amp. This indicates that the loaded car tonnage 
rating as previously calculated is all right from the standpoint 
of motor heating. 

While the preceding calculations give all of the desired results, 
the various curves may be plotted if so desired and the areas 
under the speed time and power time curves used to check the 
values of total distance and energy consumption respectively. 

Regenerative Braking. — By regenerative braking is meant the 
control of train speed by causing the motors to act as generators 
and transform the kinetic energy of the moving train into electri- 
cal energy which is fed back into the trolley or contact line. The 
advantages and disadvantages of regenerative braking and the 
modifications necessary in the design of motors and control ap- 
paratus will be discussed in later chapters. In practice regenera- 
tive braking has so far not been used in stopping trains but in 
controlling the speed of trains on heavy grades. If the trains are 
heavy and the descending grades long, considerable saving in 
electrical energy can be made, amounting in some particularly 
favorable instances to about 30 per cent. 

The power regenerated by a train descending a uniform grade 
at constant speed may be accurately calculated: 

Power output oi locomotive = Tricif) 

where the symbols used have the same significance as in for- 
mula (63). 

As the grade resistance is negative, the result will have a nega- 
tive sign indicating that the transfer of energy is from the loco- 
motive to the contact line instead of from contact line to locomo- 



LOCOMOTIVE TRAIN HAULAGE 101 

live. x\s this method does not take into account starting and 
stopping conditions, and the fact that most actual grades are more 
or less undulating, the general application of the formula gives 
results that are onh^ approximate. On account of its convenience 
it is often used by engineers in making preliminary estimates 
and in checking the results obtained by other methods. 

Where more accurate results are desired, speed, distance, 
current, and power time curves are plotted. The power time 
curve should be plotted on the negative side of the axis for the 
periods during which the motors act as generators. The regen- 
erated power at the various points along the line may then be read 
directly from the curve. The energy regenerated in descending 
a given grade may be calculated by integrating the power time 
curve for that section of the track on which the grade occurs. 
Before these curves can be plotted, it will be necessary to secure 
curves similar to those shown in Fig. 13 but giving the character- 
istics of the motor when acting as a generator. These curves 
may be obtained either from design data before the motor is built 
or by test if the motor has been constructed. In plotting the 
speed, distance, current, and power time curves the curves for 
motor action must be used when the train is taking energy from 
the line and the curves for generator action when the train is 
supplj-mg energy to the line. 



CHAPTER XII 
SUBSTATION AND POWER STATION LOAD CURVES 

Whereas the previous chapters have been devoted to the opera- 
tion of cars and trains with the ultimate object of determining 
the demands which they may make upon the power distribution 
system, it is now necessary to study the combination of individual 
train demands and their connection with the average and maxi^ 
mum loads on the substation and power station. 

The load curves of substation and power station have been 
treated simultaneously for the reason that the substation of a 
large urban railroad or a relatively long interurban line acts as a 
source of power for the surrounding distribution system and 
therefore, as far as the determination of station output and 
capacity is concerned, it matters little whether the machines 
supplying the cars are in turn furnished with electrical power 
over a high tension transmission line or whether they are driven 
by engines or turbines. 

The most convenient units in which quickly to express the 
power demands of a train were found to be ''watt hours per ton 
mile." This demand was shown to vary greatly with schedule 
speed, weight of cars, condition and profile of track, length of 
run, etc. It is clear, therefore, that except in very exceptional 
cases a single value of energy cannot be applied for the entire 
length of an interurban run from terminal to terminal. Occa- 
sionally, however, with a straight level right of way, with fairly 
constant schedule speed throughout the run and with all cars of 
about the same size and weight, an average value of energy may 
be used for all cars for the entire run and the average substation 
demand for the day determined as follows: 

U = Energy in kilowatt hours. 
Ui = Energy of car in watt hours per ton mile. 
W = Weight of car in tons. 

Sa — Length of section supplied by station in miles. 
N = Number of trips in both directions over section 
per day determined from graphical train schedule. 
Ef. = Efficiency of distribution system in per cent. 

102 



SUBSTATION AND POWER STATION LOAD CURVES 103 
The energy demand upon the substation in a day is therefore 

1000 X Eff. ^ ^ 

The average load on the station in kilowatts during the day is 

Hours operation per day 

If it were not for the excessive current taken during the accel- 
eration period as compared with the full speed running current, 
the maximum load on the station might be determined by multi- 
plying the average power required per car (average ordinate of 
the kilowatt time diagram, Fig. 23) by the maximum number of 
cars operating upon a single substation section at any one time. 
This method will usually give too low a maximum demand, how- 
ever, and it is therefore necessary to find the maximum number 
of cars starting simultaneously on a single section. For such 
cars the maximum ordinate of the power time curve, Fig. 23, 
must be used together with the average ordinate of the curves of 
such other cars as may be running upon the section at the same 
time. To determine correctly the number of cars starting at any 
one time a great deal of judgment and knowledge of local con- 
ditions is necessary in addition to a famiharity with the train 
schedule. If there be a siding located on the section it is safe to 
assume at least two cars starting simultaneously. 

While this method of determining average and maximum loads 
upon a substation has been successfully used in practice, espe- 
cially where preliminary estimates only were involved and the 
runs between stations on a given section were quite similar in all 
respects, the more detailed method outlined below is usually 
finally adopted. 

A series of speed, current, and kilowatt time curves are plotted 
for the entire road, one curve for each run between stations. If 
more than one class of service, such as local, limited, freight, etc., 
is proposed, a similar series of curves must be plotted for each. 
From the kilowatt time curves it is possible to scale off the area 
representing the energy taken by the car or train during any 
particular interval of time throughout the run. The combined 
areas of all these curves may readily be expressed in terms of 
kilowatt hours per run or, better, the portion of the run which is 
shown by the time abscissa and train schedule to be on a given 



104 



ELECTRIC RAILWAY ENGINEERING 



substation section may be thus treated. It is only necessary, 
therefore, to integrate all types of runs throughout the day on a 
given section in order to obtain the total energy and average load 
on the station in a similar manner to that of Eqs. (65) and (66). 

The problem may be carried one step farther if necessary and 
the ordinates of kilowatt time diagrams of all trains on the section 
for each increment of time may be added together to form the 
most accurate load diagram which it is possible to predetermine 
for the substation. 

Many modifications of these two methods will present them-, 
selves to the engineer as best fitted to local conditions and to the 
degree of accuracy required. Fig. 32, for example, is a load 















SUBSTATION LOAD CURVE j 






700 








































L'[i|! 


\ \ 










lil 


' 


■• i" 




®)0 










lil!! 












ill 


1 
1 


1 
1 1 













...771 


Ull! 


-J L 


._- 


._. 


__. 


. 


j'.j . 


-J 






500 






























■2 
^ inn 




























































o 


























1 














































,., 














i-i (- 








































- 1- 


1 


inn 






-1 






Ll-i 


n_f 




n n 




r 


n 


n 


r r 


m 


r 1 


"1 






"I 




"I 




n_ 












W 





















:00 8:00 10:00 13:00 3:00 
A.M. P.M. 



4:00 

Fig. 32. 



6:00 



8:00 



10:00 13:00 
A.M. 



diagram made up of rectangular areas, each representing the 
average kilowatt hour demand of all cars on one of the 12 mile 
substation sections of an existing interurban road at a given 
hour of the day. The average load on the station found by 
taking the average ordinate of this curve for the day is 69.3 kw., 
while the maximum demand from the upper curve plotted with 
reference to the possible number of cars starting simultaneously 
on the section is 655 kw. 

In plotting station load curves by whatever method, it must be 
remembered that most roads have not only the daily fluctuations 
of load which will be shown by the peaks of the load time curve 
plotted for a single day, but there is usually considerable dif- 
ference between the load curves for the various seasons of the 



SUBSTATION AND POWER STATION LOAD CURVES 105 

year, even the train schedule being changed for one of less head- 
way in the summer season. This fact, together with the possi- 
bility of sudden daily demands due to special attractions along 
the line of the interurban road, especially upon holidays, must be 
given careful attention in applying load curves to the location 
and design of substations and power stations. 

Load Factor. — The ''load factor" of a station for a given 
period has been defined as the ratio 

Average power demand . . 

Maximum power demand ^ 

although it is often considered as the ratio of average demand to 
station capacity. The load factor, as determined from the load 
curve of the substation in this particular case, is, therefore, 

69.3 



655 



= 10.6 per cent. (68) 



• A low load factor is to be avoided if possible, since it fol- 
lows that such a factor involves the use of relatively large 
station equipment operating at light and therefore low efficiency 
loads. Yet in interurban practice where the traffic is relatively 
light and the trains few in number but demanding large amounts 
of power as compared with the city systems, it is hardly possible 
to improve conditions of load factor to any great extent over the 
particular case which has been used as an illustration. An aver- 
age load factor obtained from the railway census for twenty 
representative interurban systems was 28.8 per cent., while that 
of a similar number of large city railways was 32.6 per cent. 



CHAPTER XIII 
DISTRIBUTION SYSTEM 

The circuit which the propulsion current for a car follows 
extends from the feeder panel of the substation over the out-going 
feeders and trolley to the car motors, thence through the rails 
back to the substation switchboard or, in some cases, directly to 
the negative terminal of the converter. The voltage at the sub- 
station is maintained constant, usually at 550 or 600 volts. The 
current flowing over the above circuit causes a drop of potential 
in proportion to the resistance of the entire circuit in accordance 
with Ohm's law. This fall of potential subtracted from the 
substation potential determines the voltage at the car. As the 
latter voltage should be as high and as constant as possible if 
good service is to be maintained, it follows that the resistance of 
the feeders and track return should be carefully proportioned. 
The latter will be discussed in detail under the subject of ''Bonds 
and Bonding," Chap. XVII, while this chapter will be devoted to 
the study of the overhead trolley and feeder system. 

On interurban roads and often in the city systems the trolley 
is sectionalized by the introduction of circuit breakers in the 
trolley wire which insulate one section from another. Cables 
from either side of the breaker are carried to a pole switch by 
means of which the sections may be connected together if neces- 
sary. Each section is generally supplied with power from a 
single substation through the agency of feeders paralleling the 
trolley for a portion of its length. The trolley wire itself for 
mechanical reasons is usually from No. 00 to No. 0000^ B. & S. 
gauge hard drawn copper, and is occasionally installed double 
with wires about 6 in. apart but electrically connected at every 
hanger. Where the current required is considerable this prac- 
tice is very commendable, for the second trolley replaces an equal 
amount of copper which would otherwise be installed in the 
insulated feeder and, what is of greater consequence, it eliminates 
all overhead switches and frogs in the trolley wire at sidings, the 
wires being spread as the tracks are separated, the car trolley 

^ For standards and specifications see 1914 manual A. E. R. A. 

106 



DISTRIBUTION SYSTEM 107 

always remaining on the right wire. With the size of trolley 
given, together with a well bonded track of known weight and 
resistance, the problem resolves itself into one of feeder design. 

Since the problem is necessarily treated differently for inter- 
urban and urban roads the former will be first considered. The 
minimum permissible voltage at the car under the worst condi- 
tions must first be assumed. While this voltage drops at times 
in interurban practice to 250 volts, a value of at least 350 volts 
should be used. This allows 250 volts drop in the distribution 
system under maximum traffic conditions. Reference to the 

1 >J 



r 1 1 . . , L<!'i , , "--^? , r i 



B^ A^ I Troiiey 

h h ^ 



h h H 

Fig. 33. — Continuous feeder distribution. 

train schedule will determine this maximum condition which 
usually involves two cars starting simultaneously and possibly 
others operating on the same section. Assuming the simplest 
form of distribution, Fig. 33, with the feeder paralleling the 
trolley for the entire length of the section and tapping into it suffi- 
ciently often so that they may be considered as one wire of large 
section, the following solution may be outlined: 

e = Permissible voltage drop. 
I = One-half length of section in feet. 
Zi = Distance of car (A) in feet. 
I2 = Distance of two cars at (B) in feet. 
I A = Current taken by one car at (A). 
Ib = Current taken by two cars at {B). 
Rt = Resistance per foot of track (two rails). 
RpT. = Combined resistance per foot of feeder and trolley. 
r = Resistance of copper per mil. foot. 

As in mechanics, the combined loads /^ and I^, determined 
from the current time curve, may be considered as acting through 
the equivalent distance (Ig) of the center of gravity of load from 
the substation where 

h = T , 7 — (69) 

Ia-\-^b 



108 



ELECTRIC RAILWAY ENGINEERING 



Volts drop in track (e^,.) = IgRri^A + ^b) 
Allowable drop in feeder and trolley 

epT = e - IgRrilA + Ib) 
e-kRrilA + lB) 



R 



FT 



Combined area of feeder and trolley in 
Circular mils 



r 
Rft 



(70) 

(71) 
(72) 

(73) 



Having determined the necessary combined area of feeder and 
trolley from Eq. (73), or from the wire tables, the known area 
of the trolley wire or wires may be subtracted and the necessary 
size of feeder remains. 

Assuming for illustration two cars, whose current time curves 
are represented in Fig. 22, starting 3 miles from the substation 
and a similar car running at full speed 2 miles from station. The 
trolley consists of two No. 4/0 B. & S. wires and the track is of 
70 lb. rail with 9 in. bonds equivalent to one-half the rails in con- 
ductivity. The resistance of copper may be taken as 10.6 ohms 
per mil. foot. 

Armstrong gives the resistance of third rail and track with 
the above bonding in the following table. 

Table Xlll. — Resistance of Third Rail and Track 



Wt. of rail per yard 


40 


50 


60 


70 


80 


90 


100 


no 


Third rail resistance, 


0.093 


0.074 


0.062 


0.053 


0.046 


0.042 


0.038 


0.034 


ohms per mile 


















Two track rails re- 


0.066 


0.053 


0.044 


0.038 


0.033 


0.033 


0.027 


0.024 


sistance, ohms per 


















mile. 



















I A from Fig. 22 = 672 amp. 
Ib = 160 amp. 
5280(672 X 3 + 160 X 2) 



h = 



832 



= 14,800 ft. = 2.8 miles (69) 



Volts drop in track = 832 X 0.038 X 2.8 = 88.5 volts 



(70) 



DISTRIBUTION SYSTEM 109 

Allowable drop in feeder and trolley = 161.5 volts (71) 

Rft = 832V148OO " 0-0000131 or 0.0131 ohm per 1000 ft. 

Corresponding area from wire table = 800,000 cm. 
Two 4 trolley wires = 423,200 cm. 
Feeder section = 376,800 cm. 

Either a standard 350,000 or 400,000 cm. cable might be chosen. 
If, in place of isolated sections of trollej^ the wires be continu- 
ous from terminal to terminal and the substations connected in 
parallel with one another between trolley and rail, such a prob- 
lem as that assumed above would involve the determination of 

^1 #2 



t< 1-^ >^ h >j 

Fig. 34. — Division of current between substations. 

the portion of the current per car which was supplied from each of 
the two adjacent stations. Here again the principles of mechan- 
ics may be applied as illustrated in Fig. 34 where (A) is a car at 
distances (li) and (h) from substations No. 1 and No. 2 respect- 
ivety. If the car is drawing a current (7 4) it may be safely 
assumed that its current demand on substation No. 1 is 

while the current taken from No. 2 is 

/. = 7% (75) 

With this understanding a problem in feeder calculation 
similar to the above offers no additional difficulties. 

Each half of the section in Fig. 33 was considered independently 
of the other for the reason that the feeders and trolleys of the 
two halves of the section are in parallel and therefore the vol- 
tage drop in one does not affect the other. The solution of 
a problem with the substation located at the end of the section 
would therefore be treated in a similar manner. 

In many cases, however, feeders are tapped into the trolley at 
infrequent points, thus forming a network whose calculation is 
slightly more involved. Such a condition is illustrated in Fig. 



110 ELECTRIC RAILWAY ENGINEERING 

35. The feeder is tapped to the trolley at the two points (a) and 
(6) at distances from the station of {I) and (^i) respectively. 
Two cars are starting at {B) at a distance (^2) from the station 
with total current (Z^). 

Volts drop in track = IsRrh (76) 

Allowable drop in feeder and trolley epT = e — IbRt^ (77) 

In any branched circuit problem such as this it is always most 
convenient to make use of Kirchoff's laws which may be stated 
as follows: 

First, ''At any point in a circuit, the sum of the currents 
directed toward the point is equal to the sum of those directed 
away from it." 

Second, ''In any closed circuit the algebraic sum of the (IR) 
drops is equal to that of the (e.m.f.s.)." 

While in this simple problem it is obvious without stating such 
a law that the current entering the cars at (B) is the sum of the 



-^ 



BX b] I Trolley 

I \< l-i H 

-h H 



Fig. 35. — Feeders with infrequent taps. 

two currents arriving at (B) by the two paths from (a) and (6) 
respectively, and also that the drop in potential between (B) and 
(b) must be the same by either path, yet in complicated networks, 
especially in city streets, the statement of Kirchoff's laws in this 
form is most acceptable. 

The resistance from (6) to (B) direct is that of (Z2 — ^1) ft. of 
trolley or 

RhB = RjvQ'i — h) (78) 

if (Rw) represents the resistance of the trolley per foot. The 
corresponding resistance by path (a) is 

RaB = Rw(l - h) + Rfil - h) (79) 

with (Rf) representing resistance of feeder per foot. The currents 
in the two branches may now be calculated from the two equa- 
tions 



DISTRIBUTION SYSTEM 111 

/fi = /a + h (80) 

la RbB 



lb RaB 



(81) 



With the current in each branch known, the fall of potential 
between point (b) and the car {B) ma}- be determined from either 
of the equations 

CaB = laiRoB + Rba) (82) 

CbB = IbRbB (83) 

That these two drops in voltage are identical will be shown more 
conclusively b}' substituting in (82) the value of current (7a) 
obtained from Eq. (81). 

As the total current (Is) is flowing through the feeder between 
(h) and (<S) the additional drop over this distance is 

ebs = hRph 

The total drop in the overhead conductors between substation 
and car is, therefore, 

ei = hRbB + IbRfIi (84) 

If the feeder had been tapped into the trolley at the substation 
(>S) in addition to the other taps a second network would have 
been added to the calculation, but the method of solution would 
not have been changed. In fact, am' network may be readily 
solved with the use of Kirchoff's laws if taken step by step. 

City Systems. — The principal difference between the calcula- 
tion of urban and interiu'ban feeder systems is that in the former 
it is necessary to consider a large nmnber of cars per section, each 
drawing an average ciu-rent wliich may be readily determined 
from their relative current time curves or from actual tests with 
meters on the car if the road is already in operation. Such 
sections may ordinarily be considered as uniformly loaded with- 
out serious error. 

Such a section, represented by Fig. 36, may be treated as a 
uniformly loaded beam in mechanics, and in place of using the in- 
di\'idual values of cm-rent taken by each car at a, h, c, etc., the total 
cmTent of all cars on the section combined may be considered as 
being taken from the mid-point, distant 1/2 ft. from the station. 
The correctness of tliis method may be readily proved by inte- 
grating the voltage di'ops (irdl) between the limits of zero and 



112 ELECTRIC RAILWAY ENGINEERING 

the length of the Hne {I) where {i) represents the current per foot 
and (r) the resistance per foot respectively. Having now but the 
single equivalent current to consider, the problem may be solved 
as in the case of interurban systems previously described. 

Although the limiting voltage drop is always the first con- 
sideration in railway feeders, it is well to check the safe carrying 
capacity of the cable selected by the above methods with the 
actual current which is flowing therein, the safe carrying capaci- 
ties for open wiring being readily found in any electrical handbook. 

Financial Considerations. — While the foregoing calculations 
will give the proper size of feeder to be installed for a given 
minimum potential at the car, it may be found that because of 
too great an assumed distance between stations or for other rea- 
sons the cost of the copper is prohibitive. Some consideration 



4- 



vf \ \ \ 4 Y 4^ y \ I 4^ 4' i Trolley 

abed 

Fig. 36. — Uniformly loaded distribution section. 

must therefore be given to the amount of power lost in the distri- 
bution system, and the relation, of its annual cost to the interest 
and depreciation on the copper to be installed. 

If the PR losses be summed up for each portion of the distri- 
bution section or if this same total loss be obtained from the 
product of the squared current by the equivalent resistance of 
the overhead conductors and rail return, the efficiency of the 
distribution system and the annual cost of power lost in distri- 
bution may be determined from the following equations: 

T^ff 1- . _ . Power delivered to car 

Power delivered to car -\- PR loss 



Annual cost ^^ j^^^ 

of distribu- = ( X hours per year) X 

tion loss 



Cost of power 
in cents per kw. 
hr. at d.c. busses 
of substation. (86) 

Kelvin's law states that the most economical size of feeder to 
install is that in which the annual cost of power loss is equal 
to the interest and depreciation figured on first cost of installa- 



DISTRIBUTION SYSTEM 



113 



tion. As the annual cost of power loss for a given length of feeder 
and current transmitted will decrease, while the interest and de- 
preciation charges will increase as the size of the cable increases, 
curves of these costs plotted with size of cable as abscissae will 
intersect at the most economical size of wire to be installed. 
Such curves plotted for a current of 100 amp. in 1000 ft. of feeder 
with interest taken at 6 per cent, and depreciation at 2 per cent, 
will be found from Fig. 37 to determine a feeder size of 375,000 



'55 



;S50 

"3 

2 

ft45 

o 
Q 

§ 

r 

130 



20 



§15 
O 

10 



























































KELVIN'S LAW 




















































































1 














i\ 


/ 








\ 












.s 












\ 










>v 














\ 








/ 
















\ 
























\ 


\ 


/^ 






















/ 


N 




















/ 








^^ 














/ 












' 


^^ 


^ 


OSS 




/ 

























200,000 400,000 600,000 800,000 1,000,000 
Feeder Size in Circular Mils. 

Fig. 37. 



cm. section, for which either the 350,000 or 400,000 cm. standard 
size might be selected. The calculations from which these curves 
were plotted involved a cost of power of 1 ct. per kilowatt hour 
and a cost of copper installed of 20 cts. per pound. 

Since any one of these feeder calculations taken by itself may 
give results which are unfavorable when all requirements of the 
distribution system are considered, it is the duty of the engineer 



114 



ELECTRIC RAILWAY ENGINEERING 



to calculate the proper feeder sizes necessary for a satisfactory 
line drop, to check these calculations for carrying capacity and by 
Kelvin's law and then to determine the relative weight to be 
given to the considerations of fall of potential, carrying capacity 
and relative cost of power loss in the particular system in 
question. 

Types of Systems. — The various systems of electric railway 
distribution of power may be classified with regard to structure 

. ^ Galv. Through Bolts 

2 i^"x 23^ X ^6 Galv. ■ W.I. Washers 
T 7~ M^ [—6 Rake ^_ in 24 from Top of Rail 



H x\l}£ X XG Braces Galv, 

flf^l \ i iFor 11000 Volts Use S^i'z Hi'u.V. Cross j 
1134"x ly^'x I'Top Locust Pins 

For 22000 Volts Use 3% x 4% H.P. Cross Anna 
13 X l?^"x l%"Top Locust Pina 




Fig. 38. — Typical bracket construction. 

and workmg potential. Where structure is considered it is 
found that the systems group themselves into the simple over- 
head trolley with bracket or span construction, the third rail 
and the so-called catenary construction. 

Bracket and Span Construction. — Typical forms of bracket 
and span construction are familiar to all because of their very 



DISTRIBUTION SYSTEM 



115 



general use in city and interurban installations. Fig. 38 indi- 
cates a satisfactory standard of bracket design, while Fig. 39 com- 
bines the span type of trolley suspension with a double track 
roadway and duplicate three-phase transmission lines. 

Hard drawn grooved trolley wire of 2/0 or 4/0 B. & S. gauge is 
now almost universally used with mechanical clamping ears. 
The latter are hung from the insulating hangers or cones and are 
made to grip the groove in the trolley wire by means of machine 
screws. Much time and maintenance cost is saved with this 




Special Cast Iron Socket 
^"x 4"Galv. Eye Bolts 



^/ 



5x6 Special Cross Arm 



U 



% X 5 Galv. Bolts. 
]i"s l>^"r 26"GalT. Braces. 
yi'z 3>^"Gal\-. Lag Screw. 



z 6 Special Cross Arm 

%"x 5"Galv. Bolts. 

}i"x IJs'i 26"GalT.. Braces 

i^"x 3^<"Galv. Lag Screw, 






% Mild S.M. Steel Strand Span 'Wire. 




5't\ 



% Galv. Bolt 

3H"i *}4'^ 5' I ^TroUej Wire. 
Standard Croae Arm. 
%"i ■K'Galv. Bolts. 



Trolley Wirej— 1 , 



% GalT. Bolt-N 



J^x.SjA'Lag Screw. 




% Galv. 
Bolt 



-■l- 



5^ Galv. 
Eye Bolt 



1^ X 11.4 X 36 
Galv. Braces. 



Fig. 39. — Typical span construction. 



mechanical construction as compared with the older soldered ears. 
Double insulation is provided between pole and trolley wire by 
means of an insulating hanger and the strain insulator in series. 
The latter insulators in span construction should be sufficiently 
near the trolley wire so that a broken ''live" span cannot reach 
the ground, and yet they should be sufficiently distant therefrom 
that a trolley pole cannot make contact with the live trolley wire 
and the insulated span wire simultaneously. 

Poles are usually spaced from 80 to 125 ft. apart, the lesser 
spacing being used on curves. Poles should be guyed on curves 
transversely with the line and anchors installed to take longitu- 



116 ELECTRIC RAILWAY ENGINEERING 

dinal strains at least every mile. With the present high cost of 
lumber it seems worth while to treat at least the butts of poles 
with preservative compound before installation, and it is often de- 
sirable to treat the entire pole. The poles should at least be kept 
well painted, even upon interurban lines. Iron and concrete 
poles have found a place in the city streets, principally because of 
their ornamental appearance. Corrosion can be held in check in 
the case of iron poles by frequent painting and by setting butts in 
concrete. In fact, the latter method is often used for the protec- 
tion of wooden poles even after they have begun to decay at the 
surface of the ground. 

Detailed specifications applicable to the materials used in the 
simpler types of overhead distribution systems may be secured 
from the Manual of the American Electric Railway Association 
or the Transactions of the National Electric Light Association. 

The Third Rail. — The third rail presents one solution of the 
high speed heavy current collection problem. The conductor in 
this case consists of rails well bonded together and supported on 
insulators. These insulators are placed on the ends of extra 
long ties spaced every sixth to tenth tie so that the third rail 
is at one side and slightly above the running rail. At grade 
crossings there is necessarily a break in the third rail, but the 
conductor is made continuous by means of a copper cable laid 
in conduit under the crossing. The current is collected from 
the rail by contact shoes of iron, one or more of which are 
carried by each motor car. These shoes ordinarily are pressed 
down on the head of the rail by their own weight, but in the 
case of the protected rail the latter is inverted and the contact 
shoe is held up against the rail head by means of springs. 

The third rail is supplied with power at various points by means 
of feeders as in ordinary trolley construction. The calculations 
for third rail installations are the same as for the ordinary direct 
current trolley distribution system, the resistance of the third rail, 
Table XIII, being used in place of that of the trolley wire. 

This system is used mainly in 600 volt direct current service, 
although there are several installations of 1200 volt third rail in 
operation. The Michigan Union Traction Company has gone so 
far as to use the third rail at a direct current potential of 2400 
volts on part of its system. The danger of the third rail to human 
life restricts its use to private right-of-way on interurban lines and 
to elevated or tunnel installations in cities. 



DISTRIBUTION SYSTEM 



117 



Catenary. — The catenary system of distribution was devised 
to eliminate the troubles that are necessarily attendant upon high 
speed operation when the overhead trolley is used as a collector. 
The supports at the end of each span of the simple overhead trol- 
ley wire act as rigid points in the otherwise flexible conductor, 
thus resulting in a tendency of the trolley wheel to leave the wire 
at these points, particularly at high speeds. 

For most successful high speed operation the common rule 
for a railroad track may be applied to the track of the current 
collector. The track must be level and either uniformly rigid 
or uniformly flexible. Under these conditions a current collector 
will move smoothly upon the distributing conductor. 

The catenarj^ construction is a direct result of single-phase 
alternating current distribution development. The high voltages 




Fig. 40. — Rigid catenary construction, N.Y., N.H. & H.R.R. 

used in the single-phase system make a conductor so near the 
ground as a third rail undesirable and one as large as a third 
rail unnecessary for current carrying capacity. The overhead 
trolley was therefore improved for use at high speeds, resulting 
in the so-called catenary construction. The New York, New 
Haven & Hartford system, Fig. 40, is an example of rigid catenary 
construction. Nearly all the other styles of catenary are of the 
uniformly flexible tjq^e and are much more simple and economical. 
A simple form of catenary construction, Fig. 41, consists of a 
single messenger wire and a trolley wire, the messenger wire being 
supported with the proper amount of sag by insulators on the 



118 



ELECTRIC RAILWAY ENGINEERING 



bracket arms of the poles, on cross spans, or the horizontal mem- 
bers of the bridges at the end of each span. The trolley wire is 
supported in a level position from this messenger by means of 
hangers of varying lengths. Most installations use an 11-point 
suspension of the trolley in a span of 150 ft. This construction 
was considered by some engineers as of not sufficiently uniform 
flexibility on account of the larger weight of the longer hangers 
near the span supports. The design was therefore modified by 
the hanging of a third wire, the trolley, from the second wire. 
This wire is supported by equal weight hangers which are free to 




Fig. 41. — Single catenary construction, N.Y., N.H. & H.R.R. 

move vertically. The result is a level uniformly flexible trolley, 
moving through the same vertical distance at any point in the 
span for a given pressure of the collector. The collectors used on 
catenary construction are either the ordinary trolley wheel at the 
end of a trolley pole or a roller contactor mounted on a bow or 
pantograph. These are described in a later chapter. 

From the standpoint of working potential the classes of distri- 
bution systems are : 

1. Low voltage direct current. 

2. High voltage direct current. 

3. Three-phase alternating current. ' > 

4. Single-phase alternating current. 

Under the heading of low voltage direct current (550-600 volts) 
are found practically all the city street car lines, since city ordi- 



DISTRIBUTION SYSTEM 119 

nances in this country as a rule prevent the use of higher voltages 
on public streets. A good many interurban lines are also 
equipped with this system. Ordinarily trolley suspension or 
third rail construction is used on these low voltages. 

A few years ago high voltage direct current railway systems 
were considered more or less of an experiment. Since the 1200 
volt systems have proven their merit, 2400 volt potentials have 
been installed and have already demonstrated their success. 
Most notable of these is the electrification of the Butte, Anaconda 
& Pacific Railway, an ore carrying road operating on heavy 
mountain grades in Montana. 

The feature which has made this high voltage direct current 
supply possible is the commutating pole. It has eliminated the 
commutator troubles of high voltage direct current generators 
and has made possible the successful operation of high voltage 
motors. 

Twenty-eight roads in the United States have been equipped 
since 1907 for 1200, 1500 or 2400 volt direct current operation. 
By far the greater number of these use the catenary construction. 
Their distribution systems are not essentially different from those 
operating at a potential of 600 volts. The potential is applied 
between trolley and rail and the trolley is paralleled with feeders 
whenever necessary. 

Three-phase supply of alternating current power to the electric 
locomotive has not been very popular in this countrj'' thus far, 
although wherever it has been used it has proved successful. 
Probably the most unfavorable feature is the use of at least 
two trolley wires and a motor of constant speed characteristics. 
A good example of three-phase installation in the United States is 
furnished by the Great Northern electrification of the Cascade 
Tunnel. The power is furnished at high tension to the trans- 
formers on the locomotive through the agency of the two trolley 
wires and the track. One side of the track only is bonded and 
grounded. A double trolley pole equipped with collecting 
wheels is used. In place of trolley poles one Swiss railway makes 
use of a bow with roller collectors. The trolley wires are spaced 
farther apart than in the Great Northern installation and the two 
roller collectors, separated by insulating material, make contact 
with the wires. 



CHAPTER XIV 
SUBSTATION LOCATION AND DESIGN 

There is probably no question which the engineer of a pro- 
posed electric railway system has to decide that is more depend- 
ent upon good engineering judgment and common sense than 
that of the location of substations and power stations. Many 
theoretical rules and formulas have been devised for the purpose 
of calculating the most economical location of such a station and 
many of these must be given consideration and granted their 
proper weight in the final decision, but they are of little value 
when taken alone and often lead to serious errors when given too 
much prominence or when adopted with too little reference to 
local engineering and financial relations. 

With this foreword a few of the most important of these theo- 
ries will be discussed, their relative importance being decided in 
each case by local and particularly by financial conditions. If 
the distinction between the design of alternating current sub- 
stations for single-phase lines and substations supplying 600 
volt direct current as subsequently outlined are kept in mind, the 
following considerations may readily be applied to either type 
of station. 

Substation Location. — When a substation is being considered 
whose function it is to supply power to a network of lines in a 
limited district of a large city system, one of the important con- 
siderations, as in the case of the power station, is to locate the 
station as nearly as possible at the center of gravity of the load. 
This center of gravity may be conveniently determined graphic- 
ally as in problems in mechanics as follows: Locate the prin- 
cipal centers of distribution in the district, such as prominent 
street crossings and points from which several feeders radiate, 
and determine the average load at these points as well as their 
distance apart. These may be graphically represented as in Fig. 
42, with the loads considered as weights at the corners of the dia- 
gram which is drawn to a convenient scale of distance. The 
center of gravity of the loads (A) and (B) would obviously be at 

120 



SUBSTATION LOCATION AND DESIGN 121 

(E) where d^ = OQO ^^^^^ ^^ ^^^ + ^^) ^ -^-^ miles, while 

(D) and (C) might be combined into a single load of 1650 kw. 
at (F) where 

DF _ 1000 

CF " 650 

The center of gravity of {E) and (F) with loads of 700 and 1650 
respectively located at (G) will therefore be the center of gravity 
of the system, and from the standpoint alone of supplying the 
loads most economically this should be the location of the station. 
With the more common problem, however, of locating substa- 
tions for interurban lines where the loads are usually located in a 

B-500 K.W. 




D- 650 K.W. 

Fig. 42. — Center of gravity of power damands. 

single straight line, the question to be decided is how far apart 
the stations should be placed in the single direction and there- 
fore how many and what capacity stations are necessary. The 
maximum distance between stations is limited by the voltage of 
the distribution system and in the case of the more common 600 
volt direct current distribution the distance between stations 
seldom exceeds 12 miles, each station feeding 6 miles in either 
direction. Whether this distance shall be diminished or slightly 
increased in each particular case depends largely upon the fol- 
lowing considerations. 

As the number of substations for a given road is increased, 
and therefore the distance between them diminished, the govern- 
ing factors will vary as outlined below. 

The total cost of buildings and real estate will usually increase 



122 ELECTRIC RAILWAY ENGINEERING 

in direct proportion to the increase in the number of stations. 
This statement is, of course, subject to the quahfication that such 
spacing of stations does not locate one or more of them in the 
centers of towns or cities, or in such other places as may increase 
their cost from the standpoint of high land values or expensive 
architectural effects. 

The cost of attendance will increase directly with the number 
of stations as the increased capacity of the fewer stations would 
seldom, if ever, require more attendants than the small station un- 
less the station were located in a congested city district where the 
high cost of real estate necessitated double decking the station. 

The substation equipment will cost more with the increased 
number of stations but not proportionately more. Whereas 
much of the equipment will have to be duplicated with each 
station that is added and although the cost of small units is 
greater per kilowatt capacity than that of large machines, yet if all 
the stations considered are of fairly large capacity the relay ca- 
pacity necessary for overloads of long duration and for emergency 
use will not be as great with an increased number of stations. 
This may be illustrated by assuming a total average demand upon 
all substations of 2000 kw. If two substations are decided upon, 
it would be good practice to install three 500 kw. units in each, 
or a total of 3000 kw., thus leaving one 500 kw. machine in each 
station as a relay. If, however, four stations seem advisable of 
500 kw. average demand each, it is probable that three 250 kw. 
units would be used in each station requiring the saine total 
of 3000 kw. While the switchboards, wiring, lightning protec- 
tion, etc., would therefore cost double the amount for the four 
stations, the machines and transformers would be increased 
in cost only by the increase per kilowatt of small as compared with 
large units, which increase between units of 250 and 500 kw. is not 
great. Where the total demand on all stations is much less 
than that assumed in this case, however, the small station is at a 
disadvantage with respect to relay capacity and the increased 
cost of equipment may equal if not exceed the rate of increase in 
number of stations. 

The losses in substation machinery will increase slightly 
with increase in the number of stations because of the lower 
efficiency of smaller units and the increased no-load losses of the 
larger number of machines running light or idle for a portion of 
the time as is often the case in interurban stations. 



SUBSTATION LOCATION AND DESIGN 123 

The cost of distribution copper and the losses in the distri- 
bution system will decrease with the increase in the number of 
stations, as the length and therefore the cost and resistance of 
feeders will decrease as the stations are moved nearer together. 

In order to reduce all of these quantities to common terms 
for comparison, an annual charge representing a certain pre- 
determined percentage of the first costs involved must be com- 
bined with the annual cost of attendance, maintenance, and 
power losses. This percentage of the first cost which becomes an 
annual charge in all estimates of this nature is termed a ''fixed 
charge" and involves interest on investment, taxes if any, insur- 
ance and depreciation on the equipment. This charge may be 
accurately estimated in each instance but is often assumed a total 
of 11 per cent, of the first cost whenever local conditions are such 
as not to eliminate any of the above mentioned items involved 
in its make-up. If, therefore, a curve be plotted between ordi- 
nates representing the sum of fixed charges, annual cost of power 
losses, and maintenance and abscissae expressed, in terms of 
number of substations, the total annual cost curve will result. 
Because of the fact that some of the factors are increasing and 
some decreasing with an increase in the number of stations, a 
minimum point on the curve will be found which will denote the 
proper number of substations to install and therefore the dis- 
tance between stations, considered solely from the standpoint 
of the factors involved in the curve. 

Such a method as that outlined above appears rather involved, 
requiring as it does at least a tentative station location, design of 
equipment and feeder loss calculation for each group of stations 
considered. Since the capacity alone and not the detailed plan 
of the station changes with increased number of stations, and as 
the feeder losses in an interurban system will vary approximately 
in proportion to the length of the feeders, the number of calcula- 
tions necessary for such a curve is not great and, as the cost varia- 
tions when thus graphically plotted are easily studied and com- 
pared, the solution is well worthy of serious consideration. 
Chap. XIII on the ''Distribution System" will aid materially in 
the construction of these curves. 

It will be noted that nothing was said regarding the variation 
of transmission line costs and losses in the above discussion. 
While these factors may occasionally enter the problem in the 
case of city stations with underground high tension lines, yet in 



124 ELECTRIC RAILWAY ENGINEERING 

the case of interurban installations the transmission line usually 
parallels the road for nearly the entire distance, often looping 
through each of the substations en route. With such construc- 
tion, it will be seen, the transmission line first cost and annual 
losses will not vary app];eciably with substation location, espe- 
cially for the reason that in the case of long lines with relatively 
small power requirements the transmission line wire is much 
larger than that required for any electrical considerations be- 
cause of the mechanical strength needed. Even in high tension 
underground systems the substations are usually tied together by 
such a network of primary feeders, for the sake of reliability of 
service, that the first cost and annual losses in the primary sys- 
tem may be considered practically independent of the number 
of stations providing the total output does not change. 

Another important factor which should not be overlooked, 
especially when express and freight service is contemplated, is 
the question of combining the substation, waiting station, and 
freight or express depot into one building with a material saving 
in the item of substation attendance, since the substation opera- 
tor can often attend to the other duties of the passenger station 
as well. 

If the station be not operated throughout the 24 hours the 
question of living accommodations for station attendants must 
be given some attention as the theoretical determination might 
locate the substations in localities where no attendants would 
be willing to live even though the railway company pro- 
vided living apartments in the substation building as is often 
the case. With some of the shorter systems it is possible to con- 
nect the various sections of trolley and feeders through the sub- 
station switchboard to the 600 volt direct current supply of the 
power station and thereby enable the first car in the morning to 
run over the line before the substations are started. With such 
an arrangement the operators may live in the nearest town to the 
substation. 

Substation Design. — Assuming the most common type of sub- 
station whose function it is to transform energy supplied by a 
high tension alternating current transmission line into direct cur- 
rent at approximately 600 volts, the principal factors entering 
into its design will be briefly discussed. 

With a knowledge of the load demand curve and the efficiency 
of the distribution system and with the number and location of 



SUBSTATION LOCATION AND DESIGN. 125 

substations determined, the average and maximum loads on the 
substation may be found as outHned in Chap. XII. To deciae 
upon the proper capacity of units to be installed, however, is 
largeh^ a matter of good judgment. Since it is now standard 
practice to rate electrical machinery for a possible 25 per cent, 
overload for 2 hours without overheating, the duration of the 
peak load must be studied as well as its magnitude. It must also 
be known whether or not there is a possibility of greater loads at 
any time during the year and also what the growth in power 
demand is likely to be within the next few j'-ears. With these 
facts in mind it is well to provide for the average power by the 
installation of two or more units, usually leaving one unit as a 
relay in case of emergency. This relay unit should ordinarily be 
as large as the other units in the station in order that it may take 
the place of another machine in case of breakdown. Units of 
less than 200 kw. are seldom installed and if the average load is 
less than this value, the 200 kw. machines are usually run at light 
load rather than install smaller units. This procedure involves 
relativel}^ large idle relay capacit}^ as well, but the smallest units 
are usually less reliable and offer little reserve capacity or inertia 
in case of sudden overloads. 

In the problem taken for illustration in Chap. XII the average 
demand is 69.3 kw., while the maximum demand is 655 kw. 
The low average value is due to the fact that during several rather 
long periods there is no car on the section and the unit is therefore 
running light. Further study of the curve will show that a load 
of 130 kw. is maintained for an hour at a time while peaks 
of 260 kw. exist for 15 minutes. A 200 kw. machine would 
supplj^the average load and these latter peak loads, but would not 
be of sufficient capacity for the peaks of 655 kw. caused by the 
simultaneous starting of two cars. A 300 kw. unit would there- 
fore be necessary for this station as it could withstand the momen- 
tary overload of 100 per cent. This case is a good example of the 
necessity of taking the overloads and their duration into account 
in such determinations. . 

S5nichronous Converter. — Most substations designed to sup- 
p\y direct current to a distribution system when receiving alter- 
nating current power from a high tension transmission line make 
use of the synchronous converter. This consists of a synchron- 
ous alternating current motor and direct current generator com- 
bined in a single unit with but one frame, one armature and one 



126 



ELECTRIC RAILWAY ENGINEERING 



field. It is really a direct current generator with armature tapped 
to slip rings at symmetrical points, which rings are supplied with 
alternating current as in the case of the synchronous motor. 

Without detailed analysis of the theory of the synchronous 
converter it will be seen that there is a fixed ratio between the 
direct current and alternating current voltages for a given 
machine. For converters operating upon systems of different 
phases the ratios are different, as indicated in Table XIV. The 



100 

o 90 
c 
_«> en 



70 



50 















































































EFFICIENCY OF A 750 K.W. ROTARY CONVERTER 






















































































, 


















































/ 


^ 
































^ 


^ 


































/ 




































/ 




































/ 




































1 

















































































































































30 



^0 



80 100 
Pereent Load 

Fig. 43. 



120 UO 



160 



series winding on the field of the converter cannot be made to 
vary the direct current voltage with load variations as is so 
conveniently done with the compound railway generator. It is 

Table XIV. — Voltage Ratios in Syncheonous Converters 



* "" 


No. of phases 




1 


2 


3 


G 


D. c. volts 


600 

424 

0.71 


600 

300 

0.50 


600 

367 

0.61 


600 


A. c. volts. 


212 


Ratio. 


35 







necessary, therefore, to provide some means of varying the alter- 
nating current voltage impressed upon the converter as the load 



SUBSTATION LOCATION AND DESIGN 



127 



varies. This is generally done by means of series reactance, a 
synchronous booster or induction regulator. 

The use of series reactance for compounding a converter de- 
pends upon the fact that an overexcited synchronous con- 
verter or motor will draw a leading current. The increased 
current through the series field winding of the converter with in- 
creased load merely changes the phase relation of alternating 
current to voltage but does not directly increase the voltage. 
If now inductive reactance be introduced between the step-down 
transformers and the converter, the inductive drop in potential 
through this reactance may be neutralized at heavy loads by the 
leading current drawn by the converter and the voltage impressed 



U 33000V.-- J L 33000V. J 

\AA/V\AAM/WVWA^WV IwVWWWWWWvWW 



367V. H !* 367 V.— 

hA/VVVV\AyW hAAAAA/VWV 

|3 4| ^5 6 




Fig. 44. — Three-phase delta transformer connections. 

upon the converter may thus be maintained constant or actually 
raised. While formerly these reactances were provided as sepa- 
rate units, it is now very common to introduce the reactance in 
the low voltage winding of the transformer, thus economizing 
first cost and floor space. The voltage variation possible is 
limited to about 10 per cent, in this method but it has the 
advantage of being automatic. 

The synchronous booster, as its name implies, is an alternat- 
ing current generator of the same number of phases and poles 
as the converter whose armature is connected phase by phase 
in series with the converter windings. The booster is me- 
chanically direct connected to the converter, in fact it is usually 
mounted inside the bearings and slip rings upon the converter 
shaft, while the frame adjoins that of the larger machine. The 



128 ELECTRIC RAILWAY ENGINEERING 

voltage is varied over a large range by controlling the booster 
field excitation. 

Induction regulators, which consist of automatically controlled 
variable ratio transformers, are often inserted between trans- 
formers and the converter in order that the alternating current 
voltage may be varied, but this method is more common in 
substations supplying lighting and power loads than in railway 
installations. 

Of the foregoing methods of voltage variation, the series 
reactance is cheapest but most limited in its range, the in- 
duction regulator fills a medium ground with respect to expense, 
requires considerable extra floor space and more complex cir- 
cuits, while the booster converter may be considered the most 
expensive of the three, although covering a greater range of 
voltage and taking practically no extra floor space. 

Although, as previously stated, there is in the ordinary de- 
sign of synchronous converter a fixed ratio between the vol- 
tages upon the two sides of the machine, a special design known 
as the split pole converter is an exception to the above state- 
ment. By dividing each pole into two or three radial sections 
each provided with separately controlled windings it is possible 
so to vary the flux distribution in the air gap as to produce a 
variable voltage ratio. This variation is confined within rather 
narrow limits, however, and for this reason, together with the 
greatly increased expense and complexity of control, it has 
been used more for lighting and power substations than in rail- 
way distribution. 

Not to be confused with this, however, is the recent develop- 
ment of the commutating pole or interpole converter. This 
design involves the use of an auxiliary pole halfway between 
main field poles with the winding of the former connected in 
series with the armature. By properly proportioning the 
ampere turns on the interpole so as to neutralize as nearly as 
possible the cross magnetizing effect of the armature at all loads, 
the conditions for sparkless commutation are greatly improved. 
As the commutation of the converter usually limits its rating, 
the commutating pole converter has a very high rating for a 
given size of frame. The use of these poles has also permitted 
commutation at much higher voltages, thus opening the way 
for the installation of the high voltage direct current railway 
distribution systems discussed elsewhere. One objectionable 



SUBSTATION LOCATION AND DESIGN 



129 



feature of the commiitating pole converter is the large short 
circuit currents which exist under the brushes during the opera- 
tion of starting. This difficulty has been overcome by pro- 
viding a mechanical means of lifting the brushes from the 
commutator when the machine is being started. 

Sjmchronous converters, because of the interaction of the direct 
and alternating currents in the armature, operate with higher 
efficiencies and less heating than either an alternating or direct 
current generator of the same size. The rating is therefore cor- 
respondingly higher when referred to a direct current machine 
using the same frame as indicated in Table XV. 




Fig. 45. — Three-phase "star" or ''Y" transformer connections. 

The advantages of a six-phase over a three-phase converter are 
apparent from this table, and since it is possible to supply six- 
phase power from a bank of transformers operating upon a 
three-phase transmission line, a large number of six-phase con- 
verters are now being installed. 



T.^LE XV.- 


— CoMPARATrV'E 


Ratings 


DF Converters 


D. c. generator 


Single-phase 
converter 


Three-phase 
converter 


Two-phase 
converter 


Six-phase 
converter 


1.00 


1 0.85 1 


1.32 


1.62 


1.92 



In Fig. 43 will be found an efficiency curve for a 750 kw. three- 
phase synchronous converter from which it will be noted that 
although the efficiency falls off with light loads as with all 



130 



ELECTRIC RAILWAY ENGINEERING 



other electrical machines, it may be considered constant for all 
loads above 50 per cent, of its rating. 

Methods of Starting Converters. — Three distinct methods of 
starting synchronous converters are available. In many cases 
provision for starting from either direct current or alternating 
current sources is made. If the direct current method of starting 
is adopted a starting rheostat must be provided which in turn 
will be controlled by a multi-point switch usually mounted on the 
switchboard. This switch starts the converter from the 600 
volt feeder system as an ordinary d. c. motor, gradually cutting 
out resistance until the motor comes up to speed, when the main 
d. c. switch may be closed. The speed may then be varied by 



33000 V 



■1 



^--33000V.--»| k— 33000V.--> 



367 V. 



'V. •->^ 



■ 367 V.- 



\AAA/VVV\/1 W\N\N\f\N 

1 2| Is 4 




Fig. 46. — Three-phase ''V" or '^open- delta" transformer connections. 

changing the field excitation until the a. c. side is synchronized, 
by means of the synchroscope or synchronizing lamps, as in the 
case of the synchronous motor or alternator. 

With the variable voltage alternating current method of start- 
ing, low voltage taps are taken from the bank of transformers to 
a double throw switch usually located on a separate panel near 
the converter. When the switch is thrown down a low voltage, 
usually about one-third rated voltage, is impressed on the arma- 
ture of the converter and the machine starts as an induction 
motor. As the converter approaches full speed the armature is 
supplied with full voltage by throwing the starting switch into 
the ''up" position. 

This method requires a rather large starting current at low 
power factor but has the advantage of eliminating the necessity 



SUBSTATION LOCATION AND DESIGN 



131 



of synchronizing. It is necessary to open the shunt field winding 
of the converter in several places in order that the excessive 
voltage otherwise induced in the many turns of the field by the 
large circulating currents in the armature may not puncture 
the field winding. 




Fig 



Six-phase diametrical transformer connections. 



If the auxiliary induction motor method be used a small in- 
duction motor, sufficiently large to start the converter with no 
load and bring it to slightly above synchronous speed, is mounted 



L— 33000V. J U 33000V: J 

\A/Vv/VVWVWVvWvvVVV VVWWV^AVWSA\VWVv' 



v.- 



-212 V.J 
1 2 


-212 Vt- 

sAAA/ 

3 4 




-212 V.J 

sAAA/ 

5 6 


1^212 V. J 

sA/W 

7 8 




«212V.- 

AW 




.212V.>{ 

V\AA/ 
11 12 


a d 




f. 




e 


b 








u 






\r^ 


'^^^ 




J 
e 


8^ 

-' — 


P 











Fig. 48. — Six-phase ''star" or "Y" transformer connections. 

on the end of the converter shaft. This motor is usually operated 
by means of a three-pole starting switch on the switchboard 
which is supplied with power from auxiliary transformer connec- 
tions. As the converter reaches its proper speed it is synchron- 



132 



ELECTRIC RAILWAY ENGINEERING 



ized with the transmission line as in the first case. The starting 
motor is then cut out of circuit. 

Transformers.^ — Since the supply voltage necessary for a 
converter bears a fixed ratio to the direct current voltage, step- 
down transformers are usually necessary. The secondary vol- 
tages of the latter will depend upon the method of connection 
adopted for the converter. The connections available between 
the transformers and the converter are indicated in Figs. 44 
to 50 inclusive. In all these figures a voltage of 600 has been 
assumed for the direct current side of the converter. The vol- 




FiG. 49. — Six-phase ring transformer connections. 

tages necessary between taps on the converter armature and 
those of the transformer coils are indicated in the figures. 

The primary coils may be connected in either ''star" or 
''delta," the latter having the advantage of continuous operation 
with 86 per cent, of rated capacity per transformer as the so- 
called "V" or "open delta/' in case of trouble with one trans- 
former of the bank, without change of connections. As it is 
often found desirable to raise the transmission line voltage at 
some later date, this may be very conveniently done by changing 
from "delta" to "star" if the former connection is installed at 
first. This change is possible since the line voltage with the 
"star" connection bears the ratio of 1.73 to the transformer coil 
voltage, while in the "delta" the coil and line voltages are 
identical. 

In this country preference has been shown for single-phase 

1 See also Chap. XVI. 



SUBSTATION LOCATION AND DESIGN 



133 



transformers combined into banks, usually of three each, in place 
of three-phase transformers. This is largely because of the 
increased flexibility of the sj^stem with smaller units and the 
avoidance of crippling the transformers of all phases in case of 
damage to a single unit. The rating of each transformer will 
therefore be determined as follows: 



Transformer kw. = 



Converter kw. 
3 X converter effy. 



(87) 



A bank of three transformers, each of the foregoing rating, should 
be installed for each converter or motor generator usually with 
switches in both high and low tension connections. 



33aoov.- 



[-«367 V.VJ [<367 Vr^ 



-33 000Y.- 
WWWWVWVWWWV 

h367V.-^i |-i367V.5 



< 33000 V, 

AVWWWWWWWVW 

|<367 V.VJ k367 V.vj 
101 




Fig. 50. — Six-phase double-delta transformer connections. 

Transformers may be further classified with regard to their 
method of cooling as follows: 

1. Oil cooled. 

2. Air cooled. 

3. Water cooled. 

Transformers of the ''oil cooled" class depend for their cooling 
upon the natural circulation of a comparatively large body of 
oil within the transformer case, all the heat being radiated from 
the surface of the corrugated iron cases. This construction is 
suitable for transformers of all potentials and for capacities up 
to 500 kw. 

Air cooled transformers, Fig. 51, are cooled by means of an 
air blast provided by a motor driven blower and forced through 



134 



ELECTRIC RAILWAY ENGINEERING 



the air ducts of the transformer core. This method of cooling 
requires the construction of air ducts in the floor, usually of con- 
crete, and involves the additional cost of blower outfits. It is 
suitable for all capacities but is limited to potentials of 33,000 
volts or less. 

Transformers of the third class contain a series of pipe coils 
within the case, the insulating oil circulating around the coils 
while the latter are cooled by means of circulating water within. 
This type of transformer is used for all the largest installations 
and is not limited as to capacity or voltage. 

Motor Generator vs. Converter. — A motor generator set may 
be installed in place of a synchronous converter. The motor 




Fig. 51.— Typical 7500 kw. 13,000/600 volt substation, 

may, of course, be of either the induction or synchronous type 
mounted upon the same shaft with a direct current generator. 
The advantages and disadvantages of the two types of apparatus 
for converting from alternating to direct current are as follows: 
In the case of the motor generator the ratio between a. c. and 
d. c. voltage is not fixed. For transmission voltages not exceed- 
ing 13,000 this set may therefore be operated without step- 
down transformers if the motor be wound for transmission line 
voltage. 



SUBSTATION LOCATION AND DESIGN 135 

The d. c. voltage may be readil}^ controlled by means of the 
generator field rheostat without affecting the a. c. voltage or 
power factor. 

The d. c. generator may be automatically compounded or 
overcompounded without auxiliary apparatus. The converter 
requires an external reactance in addition to the series field. 

The motor generator is not as sensitive to commutation 
troubles, especially upon sudden overloads, as the converter. 

''Hunting," or the periodic variation in speed on either side 
of an average value, with the usual accompaniments of poor 
commutation and ''arcing over" are less marked in the syn- 
chronous motor generator set because of its greater inertia, while 
the}^ are entirely absent in the induction motor set. 

The power factor of the synchronous motor generator set is 
controlled quite as easily as with the converter. The induction 
motor set, of course, has the disadvantage of low uncontrollable 
power factor. 

On the other hand, the converter has a higher efficiency. 

Its rating for a given size of frame is much higher. 

The floor area taken up is considerably less. 

Its cost is less for a given capacity although, in cases where the 
adoption of the motor generator enables the transformers to be 
eliminated, the first cost of the converter with transformers is 
about the same as that of the motor generator alone. 

Switchboard. — The typical substation switchboard consists of 
the following classes of panels: 

1. High tension line. 

2. High tension transformer. 

3. A. c. converter or motor generator. 

4. D. c. converter or motor generator. 

5. Totalizing. 

6. D. c. feeder. 

The number of panels in each class is dependent upon the size of 
station and the number of converters it contains, but all panels 
of each class are usually grouped by themselves. 

The two classes of high tension panels are usually of the remote 
control type. This is universally the case above 13,000 volts. 
With this construction the high tension switches are mounted in 
fire-proof compartments of concrete, tile or brick and maj^ there- 
fore be located at some distance from the control board. No high 
tension lines are connected with the control board, the switches 



136 ELECTRIC RAILWAY ENGINEERING 

being operated by means of auxiliary 125 volt d. c. circuits and 
the meters connected with the secondary windings of current and 
potential transformers whose primary windings are in the high 
tension circuits. Red and green lights on the switchboard panels 
indicate whether the main switches are closed or open respectively. 

The high tension line switches control the connections between 
high tension lines and the station bus bars, while each bank of 
transformers is connected to the high tension buses by means of 
the switches controlled by the panels of the second group. These 
latter switches and often both groups of switches are provided 
with inverse time limit relays which act as circuit breakers in case 
of overload, with the further provision that they may be adjusted 
to operate only after the overload has continued for a prearranged 
interval. The ''inverse" type of relay is in addition so designed 
that the greater the overload, the shorter will be the time in 
which it will open. With the transformer relays set for a very 
short interval J the high tension line switches arranged so as to 
open a fraction of a second later if the overload still continues, 
and with the relays in the out-going high tension feeders at the 
power house adjusted for an interval of 1 or 2 seconds, it will 
be seen that only those switches connecting apparatus or lines 
upon which there is trouble will be opened and the interference 
with other service reduced to a minimum. 

The meters to be installed on the first two groups of panels 
often vary widely with the personal preference of the engineer 
in charge, an average equipment probably consisting of an am- 
meter in each phase, a power factor meter and a voltmeter on a 
swinging bracket at the end of the board. 

The panels of group 3 contain all equipment necessary for 
the control of the a. c. side of the converter or motor generator, 
as the case may be, and usually include a low voltage secondary 
a. c. switch for connecting converter to transformers, motor field 
rheostat in case of a synchronous motor generator set, starting 
switch if starting motor be used, together with synchronizing and 
voltmeter plugs. The instruments usually consist of three am- 
meters and a power factor meter. A field ammeter is added 
for large synchronous machines. 

The direct current panels perform the office of connecting the 
direct current or output side of the converter or motor generator 
to the direct current bus bars. For this function three single- 
pole switches are usually employed, one positive, one negative, 



SUBSTATION LOCATION AND DESIGN 



137 



and an equalizer switch. The negative and equaUzer switches 
are often located on a pedestal or on the frame of the converter, 
thereby simplifying the switchboard connections. The field 
rheostat control of the converter or of the generator of the motor 
generator set is located on this panel together with a circuit 
breaker, a d. c. potential receptacle, and a starting switch in case 
it is planned to start the machine from the d. c. side. The meters 
are usually confined to a main ammeter and indicating watt- 




FiG. 52. — Rear of direct current generator and feeder panels. 

meter with a d. c. voltmeter on a swinging bracket. In large 
installations a field ammeter is often included on this panel. 

The totalizing panel contains instruments only and these are 
so connected as to measure the total output of the station 
between the d. c. converter panels and the outgoing feeders. An 
ammeter or indicating wattmeter and an integrating wattmeter 
are usually installed. This panel is often entirely omitted and 
the latter instrument mounted on the sub-base of one of the 
other panels. 

The out-going feeder panels may be designed to control one 
or two feeders each. Single-pole (positive) switches and circuit 



138 ELECTRIC RAILWA Y ENGINEERING 

breakers in series with ammeters make up the usual equipment 
for each feeder. 

The entire board is usually of the standard size 90 in. in height, 
including a 28 in. sub-base with panels varying in width from 
16 to 36 in. Blue Vermont marble forms the principal material 
of construction, although low voltage boards are often built of 
slate. The board should be spaced at least 4 ft. from the wall 
and the wiring at the back should be generously lighted. Where 
gallery boards of the remote control type are installed from which 
the operator may view all the machines under his control, the 
''desk type" of board has been quite frequently specified. 

Fig. 51 represents a typical General Electric six-phase syn- 
chronous converter substation with remote control switches 
and air cooled single-phase transformers. The high voltage oil 
switches are seen at the extreme left, while the low voltage a. c. 
starting switches are placed upon small panels in front of the 
transformers. Rear views of direct current generator and feeder 
panels are to be found in Fig. 52. 

Storage Battery Auxiliary. — While the storage battery is 
looked upon by many engineers and managers as an evil to be 
avoided, it certainly has its important place in the substation 
equipment of many roads. Its possible function is three-fold, 
although it is often installed for the purpose of meeting but one 
of the following requirements : 

1. To aid in maintaining constant potential. 

2. To supply all peak loads above a certain predetermined 
average. 

3. To assume the entire load of the substation for a short 
period of time. 

When the second and third functions listed above are assumed 
by the battery, its capacity must be greatly increased, yet in 
many instances batteries of sufficient capacity to fill these three 
requisites are maintained in practically all substations of the 
road. 

As the maintenance and depreciation of a battery is relatively 
high, the local problem must be carefully studied before a decision 
can be reached. Such a study should balance the fixed charges 
of the battery and accompanying control equipment combined 
with its maintenance against the fixed charges of the relay 
equipment and the extra line copper that would otherwise have 



SUBSTATION LOCATION AND DESIGN 



139 



to be installed, plus the rather intangible factors of irregular 
schedule due to variable voltage and total interruption to service. 
As an example of the use of a battery in a substation of a large 
urban railway system the Plymouth Court station of the 
Chicago Surface Lines may be cited. Two synchronous con- 
verters of 1200 kw. capacity each are supplemented by a battery 
having a capacity of 8160 amp. for 18 min. or 4080 amp. for 1 
hour. It is housed on the two upper floors of the station over the 
converters. It is regulated by a motor booster of 3000 amp. 
capacity at 70 volts. A most interesting feature of this installa- 
tion is an electric recording hydrometer which records at a 
distant point the specific gravity of the electrolyte of each cell, 
from which an idea of the condition of the battery may be ob- 




FiG. 53. — Substation with overhead entrance. 

tained. Whereas the battery might not pay for itself on the 
basis of increased load factor produced by the reduction of the 
peak load on the converters, yet when it is remembered that 
power is purchased in this case at a figure dependent upon the 
peak load supplied, the battery is of great value in smoothing 
out the load curve. 

Arrangement of Apparatus. — There is little variation in the 
arrangement of apparatus in a railway substation except in the 
extreme cases where it is necessary to locate the equipment on 
two floors. The high tension apparatus is usually confined to a 
separate room and is often located in fire-proof vaults. The 
converters, reactances, and switchboard are usually located very 
close together in a single room with the wiring either in conduit 



140 



ELECTRIC RAILWAY ENGINEERING 



embedded in the floor or of the open type supported from 
insulator racks on the basement ceiUng. The principal features 
which tend materially to alter the design of a substation are the 
overhead or underground entrances of high tension and d. c. 
feeder cables. Typical stations involving each type of construc- 
tion are illustrated in Figs. 53 and 54. 







^^Tm ^^"^m 



Fig. 54. — Substation with underground entrance. 



Wiring. — The wiring of the station is usually figured from the 
standpoint of carrying capacity only, as the potential drop for 
the short distances involved is generally negligible. The resist- 
ances of the d. c. cables between converter and switchboard 
should, however, be carefully proportioned in order to divide the 
load properly between two or more machines operating in 
parallel. The low tension wiring and the high tension cables 
up to 13,000 volts are usually insulated with rubber, paper, or 
varnished cambric and protected either with braid or a lead 
sheath. A simplified wiring diagram for a typical substation will 
be found in Fig. 55. Wiring above 13,000 volts, and often that 



SUBSTATION LOCATION' AND DESIGN 



141 




^ (^^ y[v[jA/WVVVi 



142 ELECTRIC RAILWAY ENGINEERING 

at lower voltage, is carried on line type insulators with no further 
insulation, these lines often being run in individual concrete 
or brick compartments with convenient chambers provided 
for sectionalizing or disconnecting switches and instrument 
transformers. 

Lightning Protection. — The in-coming high tension lines and 
the out-going railway feeders are each provided, just within the 
wall of the station, with a helix of wire of the same size as the 
line wire which acts as a ''choke coil" to divert high frequency 
surges to the lightning arresters connected between the coils and 
the outside lines. 

Arresters for use upon circuits of 2200 volts and less are of the 
multi-gap type. Where serious consideration must be given to 
first cost this type may be extended to as high as 33,000 volt 
circuits. 

The multi-gap arrester, as its name implies, consists of a series 
of very small spark gaps formed by placing knurled cylinders of 
non-arcing metal near one another. A sufficient number of such 
gaps are placed in series to prevent the line voltage arcing across. 
Another set of gaps, shunted with graphite resistance rods, is 
also included in the series. High frequency surges will tend to 
arc over all the gaps in order to reach ground, whereas the gen- 
erator current which follows will usually be diverted sufficiently 
through the resistance to cause the arcs over the shunted gaps 
and finally those on the series gaps to be quenched. 

The electrolytic lightning arrester, although expensive, is now 
universally recognized as the best protection from lightning for 
high voltage circuits. It consists of a series of aluminum trays 
separated slightly from one another by a space filled with an 
hydroxide solution. If a current is passed daily through this 
set of trays in series a thin film of aluminum hydroxide is formed 
on the plates which will offer a high resistance up to approximately 
400 volts per tray. When this voltage is exceeded a current 
is readily conducted through the various elements from line to 
ground. The group of trays is mounted in a steel tank filled 
with transformer oil for insulating and cooling purposes, as 
indicated in Fig. 56. 

Since such a series of metal plates separated by a dielectric will 
act as a condenser on an alternating current system, thereby 
drawing a rather objectionable charging current from the line, 
one or more horn gaps are usually introduced to break the circuit. 



SUBSTATION LOCATION AND DESIGN 143 

These are adjusted to arc at critical voltages and relieve any 
abnormal potential whitih may exist on the line. 

The disadvantages of this type of arrester, aside from its high 
first cost previously mentioned, are the regular charging necessary 
to maintain the insulating film on the aluminum trays and the 
tendency to freeze in exposed installations, 

A still more recent arrester which is particularly adapted for 
exposed conditions takes the form of a condenser bushing. It 



Fig. 56. — Sectional view ef aluminum cell lightning arrester. 

consists essentially of a number of metal cups in series with a 
resistance mounted upon an insulating bushing which in turn is 
supported upon a metal rod. Porcelain bushings insulate one 
cup from another. The upper cup of the series is connected 
to the line and the supporting metal rod is grounded. This 
apparatus may be considered therefore as a series of condensers 
between line and ground, while each is in itself a shunted con- 
denser with respect to the ground. The breakdown of the upper 



144 



ELECTRIC RAILWAY ENGINEERING 



condenser, due to abnormal potential, exerts excessive voltages 
upon the remainder of the series and the complete discharge takes 
place. The principle of operation is not unlike that of the elec- 
trolytic arrester except that the insulating j&lm is permanent. 
It has the disadvantage of not being self healing in case the insu- 
lation is punctured. 

Portable Substations. — On many roads traffic demands be- 
come excessive upon certain days or weeks of the year on differ- 




Portable substation. 



ent sections of the line. A means of meeting this local and 
temporary demand for power has been found in the "portable 
substation," Fig. 57, which usually consists of a box car with a 
converter, transformers, switchboard, etc., complete and ready 
for connection to the high tension lines at any point on the 
system and capable of operating in parallel with the permanent 
station on any desired trolley section. Such a portable station 



SUBSTATION LOCATION AND DESIGN 



145 



has proved a means of providing good service under extreme 
conditions not only, but has protected the regular equipment 
from damage due to serious overload as well. 

High Voltage Direct Current Substations. — Within the last 
few years the high voltage direct current railway system has 



Swing. 


2C.S.F. 


ing 


Puuels 


Jracke 


1200 V. 




333 A. 



2 C.S.G. Panels 1200 V. 
400 Kw. 



CD.G. 
2 A T V Panels 125 V.D.C. 6 Kw. 13200 V.A.O. 
^•^•^- 400 Kw. 

Incoming Lines 




iKqualizer 



SyncbronouB 
Motor 
f— - Bus (Grounded) 



Fig 



Wiring diagram of high voltage direct current substation. 



been developed and many interurban roads are now operating 
on from 1200 to 3000 volts. This increase of voltage decreases 
the first cost of installation as it reduces the number of sub- 
stations necessary as well as the amount of distribution copper 
required. A more detailed comparison of its cost and ad- 
vantages will be found in a later chapter. 

10 



146 ELECTRIC RAILWAY ENGINEERING 

The substation design for such a system is not materially 
different from that outlined above except in the case of the con- 
verting equipment. Two standard 600, 1200, or 1500 volt 
machines, connected in series, are usually installed for this 
service, the negative terminal of one unit being connected to the 
rail while the positive lead from the second machine is carried 
to the switchboard bus bars and thence through feeder panels 
to the feeders and trolley. The wiring diagram for such a 
station will be found in Fig. 58. It should be noted that in this 
installation no transformers are used, although the synchronous 
motor of the motor generator set operates at 13,200 volts. 

Single -phase Alternating Current Substations. — In systems 
where single-phase alternating current is supplied to the car in 
place of direct current there is, of course, no demand for the 
conversion of alternating current to direct current in the sub- 
station. On long lines, however, substations are still necessary 
to reduce the potential of the transmission line to that suitable 
for the trolley, the latter voltage usually being 6600 or 13,000 
volts. Such substations, involving only transformers, lightning 
protection and switches, require no attendants and are therefore 
very small and simple in design as compared with the stations 
previously considered. Automatic oil switches are usually 
installed in both primary and secondary circuits of the step-down 
transformers, although in this case the time element of the auto- 
matic relay is adjusted for a greater time interval than those at 
the power station in order that the latter switches will open first 
in case of trouble. This method, which is just the reverse of that 
in converter substations, is adopted to avoid frequent trips to the 
substation to close switches. 

Outdoor Substations. — The successful operation of small out- 
door substations for lighting service has encouraged larger 
and higher voltage designs, especially in single-phase systems in 
which no converting apparatus is necessary. Even in the latter 
cases the high tension bus bars, lightning arresters and trans- 
formers may be installed outside the station, while the low vol- 
tage apparatus requiring supervision is placed under cover. The 
advantages of such construction are lower first cost, less space and 
building capacity, and less life and property hazard. Contrasted 
with these must be considered the greater difficulty of inspecting 
and repairing apparatus located out of doors and the greater 
danger of its being molested by trespassers. 



SUBSTATION LOCATION AND DESIGN 



147 



Transformers and remote controlled oil switches or circuit 
breakers must be specially designed and constructed to keep out 
all moisture and even the effects of condensation of moist air 
within their cases. Self cooled, oil insulated transformers may 
be operated with greater loads when located outdoors in most 
climates, especially if shaded from the sun in hot summer 
weather. When water cooled, care must be taken to avoid freez- 
ing of the circulating water in winter at light loads, although the 
oil itself will usually be sufficiently protected by the heat gen- 
erated by the core losses alone. 

With reference to first cost, the following estimate will in- 





g|^. 






r 


^" 1 




hI 


Im 


ppp ^ ^^pM^r?^^^' 


JS. ■ .. 


. ■ ,.!■■-. ■- * 




<^- 



Fig. 59. — Single-phase outdoor substation. 

dicate the gain to be experienced in a 3000 kw. 600 volt motor 
generator station supplied from a 22,000 volt transmission line 
when the high tension equipment is placed outside the building. 

While such a station shows a gain of but 12 per cent., a simi- 
lar change on a substation requiring no converting machinery 
may be accompanied by a saving as high as 30 per cent. 

In Fig. 59 will be found a halftone of one of the new outdoor 
substations of the New York, New Haven & Hartford Railroad 
which represents probably the largest railway outdoor sub- 
station yet installed. The 2000 kw. 22000/11000 volt single- 
phase water cooled transformer with weather-proof insulating 



148 



ELECTRIC RAILWAY ENGINEERING 



bushings is seen at the extreme left, while the oil circuit breakers 
and electrolytic lightning arresters provided with weather-proof 
tanks are indicated in the central and right-hand portions of the 
figure respectively. 



Table XYU 


— Estimated Costs of Substations 




Indoor 


Outdoor 


Building 


$21,835 

20,000 

15,000 

48,000 

4,500 


$7,480 
20,200 


Switchboard 


Transformers 

Motor generator sets 


16,000 

48,000 

4,500 


Exciters 










$109,335 


$96,180 



Substation Cost. — The following working estimate prepared 
to cover the total cost of four substations of the 600 volt direct 
current type for a 63 mile interurban line in the South may be 
useful in determining the relative cost of substation equipment. 
As each station contains one synchronous converter of 300 kw., 
the costs may be figured on a basis of 300 kw. per station. 

4 Substation buildings, @ $4.00 kw $4,800 

4 Converter foundations, 150 yd. @ $8.00 1,200 

4 Transformer banks, 1320 kw. @ $10.00 13,200 

4 Converters, 1200 kw. @ $16.00 19,200 

Freight and erection 3,000 

4 Switchboards, 4 panels each 8,800 

Freight and erection 1,600 

Wiring, @ $1.50 per kw 1,800 

High tension switch cells 1,000 

Lightning protection 2,400 

Total, @ $47.50 kw $57,000 

Whereas the discussion in this chapter covers the principal 
features of substation location and design, many special features 
with regard to operating costs and the function which the sub- 
station has to play in the various types of distribution systems 
will be considered briefly in succeeding chapters. 

lA. I. E. E., Vol. XXVIII (Randall). 



CHAPTER XV 
TRANSMISSION SYSTEM 

The necessity for greatly detailed calculations in designing 
high tension transmission lines for railway systems is often ex- 
aggerated. The fact that the careful predetermination of all 
characteristics of such a transmission Une is unnecessary, when 
compared with the careful study required in connection with a 
line for the transmission of power for lighting or even for the 
very high voltage long distance transmission of energy in large 
quantities from hydro-electric plants, will be made clear by the 
following outHne of conditions generally pertaining to the rail- 
way system. 

In the first place the close regulation of voltage is both un- 
necessary and impossible. The sudden variations of power de- 
manded by cars, especially upon an interurban system, must 
inevitably mean variable voltage, and with such voltage variation 
on the distribution system there is Httle need of the closest 
possible regulation on the transmission line. 

Nor is the service impaired by such voltage variation as would 
be suicidal to the lighting substation. The motorman or pas- 
sengers upon an interurban car will hardly notice a 10 per cent, 
voltage variation, while sudden variations of 2 or 3 per cent, are 
to be avoided if possible in connection with incandescent lighting, 
particularly as the intensity of light varies throughout a greater 
range than the voltage. The lighting of interurban cars is of 
course greatly impaired by poor voltage regulation and this is 
one of the features that is receiving a great deal of just criticism 
from the traveling pubhc. Its remedy, however, lies in making 
the Ughting independent of trolley voltage and not by attempting 
to regulate the latter more closely. 

The regulation of transmission lines is greatly affected by low 
power factor. The addition of induction motors or arc hghting 
systems which operate at low power factors to long distance 
transmission lines involves very careful design and costly regu- 

149 



150 ELECTRIC RAILWAY ENGINEERING 

lating apparatus if lighting loads are to be successfully supplied 
by the same line. In many such instances synchronous motors 
are installed, often without direct financial return to the company, 
in order that the power factor may be properly controlled. Such 
control is present in the railway substation in either the synchro- 
nous motor generator set or converter and with little practice the 
substation attendant can maintain very nearly unity power factor 
on the transmission line and thereby aid its regulation to a great 
extent. 

Many of the limiting factors in high tension line design, such 
as the pin type of insulator, corona losses, troubles involved by 
wide spacing and long spans, etc., are introduced only when the 
voltage becomes higher and the amounts of power become much 
greater than those involved in the major part of the interurban 
transmission. In fact a census of transmission lines for railway 
purposes only would probably reveal the fact that an extremely 
small percentage of these lines are above 33,000 volts. At this 
voltage two parallel three-phase circuits on pin type insulators 
and wooden poles, carrying in addition the distribution feeders 
and trolley brackets, represent common practice. Such a line in 
the Middle West has for years been satisfactorily operating an 
interurban system 110 miles in length at 33,000 volts. In such 
design simple electrical and mechanical considerations are alone 
involved. 

For the above reasons, therefore, and because of the very able 
treatises in complete volumes devoted to the details of this sub- 
ject, an exhaustive study of transmission line design will not 
be attempted in these pages. 

The three-phase system of alternating current transmission 
has been standardized almost exclusively for railway work. This 
is principally because polyphase apparatus is necessary for sub- 
station units in large sizes and in addition because the three-phase 
system requires but three-fourths the copper of the single-phase 
installation. Other polyphase systems, although more economical 
in copper in some instances, have not found favor largely because 
of the complication introduced by the greater number of wires. 
While six-phase substation apparatus was shown in the preceding 
chapter to be highly desirable, the possibility of its operation from 
a three-phase line has introduced no serious consideration of 
six-phase transmission. For these reasons, therefore, three-phase 
transmission only will be herein considered. 



TRANSMISSION SYSTEM 151 

Mechanical Strength. — Owing to the fact that calculations 
of the proper size of wire for transmission lines, based on Kelvin's 
law, voltage regulation, and carrying capacity, in most cases 
result in a wire too small to withstand the mechanical stresses 
incurred by ordinary line construction and weather conditions^ 
the mechanical strength of the line may well be considered first 
and the size of wire checked in accordance with the electrical 
considerations later. No wires smaller than No. 4 B. & S. 
hard drawn copper or its equivalent in tensile strength should 
be used, for mechanical reasons. If aluminum be used it should 
be remembered that for the same size aluminum weighs about 
30 per cent, and has a resistance of 1.67 times that of hard drawn 
copper. Aluminum costs considerably less than copper for the 
same conductivity and melts at a much lower temperature. It 
also has a greater coefficient of expansion causing greater varia- 
tion in sag wdth change of temperature. It is difficult to solder, 
is quickly attacked by gases in the atmosphere and has a tensile 
strength of approximately one-third that of copper. In spite 
of its many disadvantages aluminum is used to a considerable 
extent for line construction largely because of its low^ cost and 
light weight. Joints are made mechanically by overlapping the 
ends in an oval sleeve and twisting the sleeve and wire ends to- 
gether without solder. On account of its large diameter for a 
given conductivity the total wind pressure on a line is greater, and 
because of its low melting point it is more likely to melt apart 
than is copper in the event of an arc forming between wires. 

The question whether one or two parallel three-phase lines 
shall be installed, one for the purpose of acting as a relay for 
the other in case of breakdown, is an open one and is generally 
decided by the personal preference of the engineer in charge. If 
a single line only be installed it is usually mechanically stronger 
and therefore better able to withstand abnormal strains. In 
this case the wires are spaced at the vertices of an equilateral tri- 
angle wdth one wire on the pole top and the two lower wires on a 
single cross arm. If two circuits are employed two arms are used 
and one circuit is installed on either side of the pole. Such con- 
struction permits repairs to be made on one of the lines with the 
other in operation when the voltage does not exceed 33,000 volts. 

No particular specifications need be made for the poles, which 
are also used for the trolley span wires, feeders, and probably 
signal and telephone circuits as well, except that they must be 



152 ELECTRIC RAILWAY ENGINEERING 

sufficiently high to give sufficient clearance to the high tension 
wires during the period of maximum sag and that they be at least 
7 in. in diameter at the top. The forces acting on the poles due 
to the presence of the high tension line are: 

Vertical downward force due to weight of conductors with 
possible ice sheath and vertical component of wire 
tension. 

Bending moment due to angle in line or with one or more 
wires broken. 

Bending moment due to wind pressure on pole and ice 
sheathed wires. 
Although these forces may be readily calculated by means of 
the fundamental laws of mechanics, it is safe to assume that 
there is a sufficient factor of safety with a properly constructed 
pole line sufficiently heavy for the trolley and feeder installation 
for the reason that the latter acts as a longitudinal anchor guy in 
case of a broken high tension wire, and owing to the further fact 
that the possible strains on the high tension line are generally 
small as compared with those incurred by the feeder and trolley 
construction. 

Electrical Considerations. — Considering the large number of 
railway high tension lines using No. 4 B. & S. wire, and remember- 
ing that this should be a minimum for mechanical reasons, it will 
probably save time in calculation to assume this size at the start. 
A convenient spacing for wires not exceeding 33,000 volts is 
36 in. With these dimensions in mind it will be remembered 
that in determining the regulation of an alternating current 
line the impedance must be considered in place of the resistance 
which is used in direct current calculations. Impedance may be 
considered as the resultant of the resistance and the reactance 
of the line combined at right angles. In other words, 



where Z = Impedance of line in ohms. 
R = Resistance of line in ohms. 
X = Reactance of line in ohms. 

The reactance {X) of a transmission line is partly due to in- 
ductance (L), which in turn is dependent upon the cutting by 
the wire of lines of force set up by the current in the wire, and the 
capacity (C) which is the effect due to the wires acting as the 



TRANSMISSION SYSTEM 153 

plates of condensers with the air as a dielectric medium between. 
Since the formulas for these quantities given below show that the 
capacity is decreased and the inductance increased as the wires 
are moved apart and also as the size of wire is decreased, these 
two functions of reactance will be seen to be opposed to one 
another, one neutralizing the other to some extent. Since the 
capacity effect is relatively small, especially on the average short 
line of the interurban railway operating at moderate voltage, 
it will be neglected in the first determination of regulation and 
the error introduced by such a procedure pointed out later. 

As the theoretical proof of the formulas for line inductance and 
capacity is beyond the scope of this book and as their methods 
of derivation are included in most theoretical treatises on electri- 
cal engineering, they are listed below without proof. 

0.0776 I 



C = 



d (89) 



2 log. 10^ 

L = 0.000322 (2.303 logio(-) + 0.25)1 (90) 

where L = Self inductance per wire in henries. 

d = Distance between wire centers in inches. 

r = Radius of wire in inches. 

C = Capacity between one wire and neutral point in 

microfarads. 
I = Length of circuit in miles. 

Considering only the resistance and inductive reactance of the 
line at present, the latter may be found from the equation, 

Xl = 2irfL (91) 

where Xl = Reactance due to inductance in ohms. 
/ = Frequency in cycles per second. 
L = Inductance from Eq. (90) in henries. 

Tables giving such of the inductive reactance values and re- 
sistances as will be needed in railway transmission line calcula- 
tions are given below. 

Since the power factor at the substation may be maintained 
at approximately 100 per cent, by control of the field of the 
synchronous converter or motor generator, such a power factor 
may be safely assumed in line calculation. In fact it would not 



154 



ELECTRIC RAILWAY ENGINEERING 



introduce a serious error to neglect reactance of the line entirely 
and solve the problem as if for a direct current system, since even 
the effect of line reactance may be overcome by careful regulation 
of the substation apparatus as explained above. 



Table XVII. ^ — Inductive Reactance of Single Wire in 


Ohms 


PER 


Mile 










Spacing inches 25 cycles 




Size wire 


















24 


36 


48 


60 


72 


" 


.. 


108 


120 


150 


350,000 cm. 


.235 


.255 


.270 


.280 


.290 


.298 


.304 


.310 


.315 


.327 


300,000 


.238 


.258 


.273 


.285 


.294 


.301 


.308 


.314 


.320 


.330 


250,000 


.242 


.263 


.278 


.289 


.298 


.305 


.313 


.319 


.324 


.335 


4/0 B. & S 


.248 


.268 


.283 


.294 


.303 


.310 


.318 


.325 


.329 


.340 


3/0 


.254 


.274 


.289 


.300 


.309 


.317 


.324 


.330 


.335 


.346 


2/0 


.259 


.280 


.294 


.306 


.315 


.323 


.329 


.335 


.341 


.352 





.265 


.286 


.300 


.311 


.321 


.329 


.335 


.341 


.347 


.358 


1 


.271 


.292 


.306 


.318 


.327 


.334 


.341 


.347 


.352 


.364 


2 


.277 


.297 


.312 


.323 


.332 


.340 


.347 


.353 


.358 


.370 


3 


.283 


.303 


.318 


.329 


.338 


.345 


.352 


.359 


.364 


.375 


4 


.289 


.309 


.324 


.335 


.344 


.352 


.359 


.365 


.370 


.381 


6 


.300 


.321 


.335 


.347 


.356 


.363 


.370 


.376 


.381 


.393 



Table XVIII. ^ — Resistance of Copper and 


Aluminum at 70°F. 




Ohms per mile 


Size wire 




Copper 


Aluminum 


500,000 cm. 


0.109 


0.176 


450,000 


0.121 


0.196 


400,000 


0.137 


0.221 


350,000 


0.156 


0.252 


300,000 


0.182 


0.294 


250,000 


0.219 


0.353 


4/0 B. & S. 


0.258 


0.417 


3/0 


0.326 


0.526 


2/0 


0.411 


0.664 





0.518 


0.837 


1 


0.653 


1.055 


2 


0.824 


1.330 


3 


1.039 


1.678 


4 


1.309 


2.116 


6 


2.082 


3.309 



Standard Handbook, Section 11, p. 40. 



TRANSMISSION SYSTEM 155 

Voltage Determination. — The voltage and current per wire 
must now be determined. They are principally dependent upon 
the substation input and distance of transmission. 

In deciding upon the proper voltage for the transmission line 
as well as in selecting electrical equipment it is necessary to take 
into consideration the standards established by the manufacturers. 
Primary substation voltages have been standardized as follows: 
11,000, 19,100, 33,000, 66,000, and 120,000 volts. The two lower 
potentials are most often used with ''delta" connections while 
voltages of 33,000 and 66,000 are usually obtained with ''star" 
connected transformers. It should be noted that the three lower 
voltages bear the ratio of \/s to one another, thus permitting the 
next higher standard voltage to be obtained by changing connec- 
tions of transformers from "delta" to "star." For a rough 
selection of the voltage to be first used for calculation, 1000 
volts per mile of transmission are often used. As local condi- 



Im-Xj 



Eg \u} R 

Fig. 60. — Vector diagram for transmission line regulation unity 
power factor. 

tions enter into the problem to a marked degree, and since it is 
almost impossible to express intelligently in equation form all the 
factors entering into the selection of the proper voltage from the 
standpoint of regulation, first cost, and economical operation, it 
seems advisable to select two of the nearest standard voltages by 
the above rule and compare the resulting calculated data of the 
two cases before finally determining upon the best operating 
voltage. 

Regulation. — The transmission line calculations are usually 
based upon the combined substation inputs supplied by a single 
line at full rated load although, if the number of substations be 
large, it may be found from a study of their load curves that their 
maximum loads do not occur simultaneously and that the total 
demand on the transmission line may be considerably below the 
summation of the substation ratings. The rated output of the 
substation transformers was found in Chap. XIV, Eq. (87). The 
input to the station may be obtained from the above by dividing 




156 ELECTRIC RAILWAY ENGINEERING 

the output of all transformers by the transformer efficiency which 
may be safely assumed for large transformers at full load as 98 
per cent. 

The current per wire on the transmission line is therefore 

_ Kw X 1000 ^^^^ 

^^- V3^cos<A ^^^^ 

where Iw = Current per wire in amperes. 
Kw = Substation input in kilowatts. 
E =■ Voltage between wires at substation, 
cos cf> = Power factor of load at substation. 

For this calculation (cos <^) is taken as unity as explained above. 
The impedance of the transmission line may now be found 
from Eq. (88) if values of reactance and resistance from Tables 
XVII and XVIII for No. 4 B. & S. wires spaced 36 in. apart be 
substituted. The voltage drop on the line is 

e = IwZ (93) 

These relations, including the generator voltage (Eg) are shown 
in Fig. 60 from which the value of Eg may be derived. 



Eg = \(Es + IwRr + (Iw^l)' (94) 

where (Eg) represents substation voltage between wire and neu- 

tralor^ 

Regulation = —^-^ — - (95) 

If less than unity lagging power factor be assumed as in 
the case of an induction motor generator set for example, other 
conditions remaining the same, a larger current (/V) would have 
resulted from Eq. (92) and the voltage diagram would appear as 
in Fig. 61, the resulting generator voltage being 



E'g = -^iEs COS cf> + rwR)' + (Es sin <t> + FwXlY (96) 
As before, the percentage regulation may be obtained from the 
equation 

Regulation = — ~ (97) 

If the regulation from either Eq. (95) or (97) is unreasonably 



TRANSMISSION SYSTEM 



157 



high, a suitable value, say 10 per cent., may be substituted back 
into the equation and corresponding values of Eg or E'g found 




ImjXj 



E.COS0 



Fig. 61. — Vector diagram for transmission line regulation lagging 
power factor. 

from which the correct value of (R) may be calculated by means 
of Eq. (94) or (96) and the proper size of wire obtained from 
the wire table. 

As a concrete illustration of these two approximate methods of 
obtaining regulation, assume the following conditions: 

Substation input = 1500 kw. 
Power factor =100 per cent. 
Length of line = 50 miles. 

Using No. 4 wire and a substation voltage of 33,000, there results: 

R = 1.309 X 50 = 65.4 ohms. 
Xl = 0.31 X 50 = 15.5 ohms. 

33000 



Es per terminal = 



V3 



19,100 volts. 



Z = "^(65.4) 2 + (15.5)2 = 67 ohms. 
1500000 



w 



33000V3 



26.2 amp. 



Eg = 'V(19,100 + 26.2 X 65.4)2 + (26.2 X 15.5)^ = 20,820(94) 



Regulation = 



20820 - 1 9100 
19100 



= 9 per cent. 



(95) 



Now suppose the power factor to be lowered to 85 per cent, 
by low field excitation of synchronous apparatus or the operation 
of an induction motor generator set. 



158 ELECTRIC RAILWAY ENGINEERING 

1500000 
^ - = 33000V3 X 0.85 = '''' ^'^^' ^''^ 

E', = ^/("l9,100 X 0.85 + 30.9 X 65.4)^ + (19,100 X 0.527 + 
30.9 X 15.5)2 = 20,900 (96) 

^ , ^. 20900- 19100 ^,^ ^ ,^^. 

Regulation = uy\c\r\ ^ P^^ cent. (97) 

Both the regulation for 85 per cent, power factor and unity 
power factor are sufficiently small for railway service and the con- 
ditions of size of wire, voltage, spacing, etc., may be tentatively 
decided upon and checked further with regard to Kelvin's law, 
carrying capacity, etc., as explained under '' Distribution System." 

Capacity Effect. — Since, however, the capacity has been en- 
tirely neglected in the above calculations, the error introduced 
by such omission should at least be pointed out. 

As previously explained, the line wires act as plates of a con- 
denser and thus draw a leading ''charging" current from the 
power house just as an infinite number of small condensers would 
do if connected in parallel across the line wires throughout their 
entire length. As such a uniform distribution of capacity in- 
volves a constantly changing charging current, power factor, and 
voltage throughout the entire length of the line, which condition 
can be represented only by a rather involved mathematical 
equation, it has been shown by Steinmetz^ that this capacity effect 
may be represented sufficiently accurately by locating one-sixth 
of the total capacity at either end and two-thirds in the middle 
of the line. In fact, little error is introduced if the entire 
capacity is considered in parallel with the line at either the 
generator or receiver end. Adopting the latter assumption, the 
equations below show the method of derivation of the values in 
Table XVII and the calculation of charging current for any as- 
sumed length of line, voltage, and wire spacing. 

The values of charging current in Table XIX which are de- 
pendent upon a voltage between the line wires and the neutral 
point of 100,000 volts for a single mile of line at 25 cycles fre- 
quency and a given spacing are obtained by substitution in 
formula (89). 

For example, assuming the conditions of the transmission 
problem above, 

^ " Alternating Current Phenomena," by Dr. C. P. Steinmetz. 



TRANSMISSION SYSTEM 
0.0776 



^^S^« (0:102) 



= 0.0153 microfarad 



159 



(90) 



between 1 mile of No. 4 wire and neutral with 36 in. spacing 

2TfCE 



Ic = 



W 



(98) 



If Ic = Charging current in amperes per mile at 100,000 volts. 
/ = Frequency in cycles per second. 
C = Capacity in microfarads per mile. 
E = 100,000 volts. 

27r X 25 X 0.0153 X 100,000 



10' 



= 0.239 amp. (98) 



Table XIX. — Charging Current of Single Wire in Amperes per 
Mile per 100,000 Volts, 25 Cycles 



Size wire 


Spacing in inches 


stranded 


24 


36 


48 


60 


72 


84 


96 


108 


120 


150 


350,000 cm. 


.329 


.300 


.283 


.270 


.261 


.254 


.248 


.243 


.239 


.230 


300,000 


.323 


.295 


.278 


.267 


.258 


.250 


.245 


.240 


.236 


.227 


250,000 


.316 


.290 


.274 


.262 


.253 


.246 


.241 


.236 


.232 


.224 


Solid 4/0 B. & S. 


.301 


.278 


.262 


.253 


.243 


.239 


.232 


.228 


.224 


.210 


3/0 


.295 


.272 


.257 


.245 


.239 


.234 


.228 


.224 


.220 


.21.2 


2/0 


.287 


.265 


.251 


.242 


.232 


.228 


.224 


.220 


.217 


.209 





.279 


.261 


.246 


.237 


.229 


.225 


.220 


.217 


.212 


.206 


1 


.275 


.251 


.242 


.229 


.223 


.220 


.217 


.212 


.209 


.203 


2 


.268 


.250 


.237 


.226 


.221 


.217 


.212 


.209 


.206 


.199 


3 


.264 


.246 


.229 


.225 


.217 


.212 


.209 


.206 


.203 


.196 


4 


.255 


.239 


.226 


.220 


.214 


.209 


.206 


.203 


.200 


.193 


6 


.245 


.231 


.220 


.212 


.204 


.201 


.198 


.195 


.191 


.189 



This value will be found in Table XIX opposite No. 4 wire 
with 36 in. spacing. 

The charging current for any other voltage {E') between wire 
and neutral and for any other length of line (I) is, of course, 

27rfCE'l 



I'o = 



or 



I'c 



100000 X 10« 

Table value X I X E' 
100000 



(99) 
(100) 



160 



ELECTRIC RAILWAY ENGINEERING 



Again, considering the concrete illustrative problem at unity 
power factor the charging current for the line is 



I'o = 



0.239 X 50 X 19100 
100000 



= 2.28 amp. 



(100) 



It will be seen, therefore, that the charging current with this 
particular load and design of line is quite an appreciable per- 
centage (8.7 per cent.) of the full load unity power factor current. 
The charging current might be decreased somewhat by separating 
the wires. As this current is independent of load its percentage 
will decrease of course as the load increases. 

In refiguring the regulation this time taking the charging cur- 
rent into account, it must be remembered that this current leads 
the voltage at the substation {Eg) by 90 deg. The vector dia- 
gram of voltages is therefore represented by Fig. 62 where the 




\w^l 



Fig. 62.- 



-Vector diagram for transmission line regulation with 
charging current. 



direction of the charging current vector and therefore of the 
vector of resistance drop due to charging current {IcR) is vertical 
and the reactance drop due to charging current {IcX£), horizontal 
since (Es) is horizontal. The generator voltage {E"g) may be seen 
from the geometry of the diagram to be 



E", = V(^3 + IwR - IcXlY + {IwXl + IcRY (101) 

which is obviously less than {Eg), Eq. (94), since the charging 
current tends to neutralize the effect of line inductive reactance, 
thereby reducing the regulation to the value 



Regulation = 



E'\ - Es 
Es 



(102) 



Substituting the numerical data of the above problem 

E''g = \/(19,100 + 26.2 X 6 5.4 - 2.28 X 15.5)^ + (26.2 X 

15.5 + 2.28 X 65.4)2 = 20,760 volts (101) 



TRANSMISSION SYSTEM 161 

Regulation = Touin "^ ^'^ P^^ cent. (102) 

A similar diagram might be drawn and the regulation calcu- 
lated showing the effect of charging current with low initial 
lagging power factor by adding the triangle of charging current 
fall of potential to the diagram, Fig. 61, with the vector (IcR) 
leading (Es) by 90 deg. 

Comparing the regulation found by taking charging current 

into account, Eq. (102), with that which neglected that particular 

effect, Eq. (95), the error will be seen to be 

^ 9- 8.7 _ 

-brror = — ^r^ — = S.o per cent. 

which ma}^ safely be neglected in most railway work, especially as 
the approximate method gives the highest and therefore the most 
conservative estimate of the regulation. 

It is believed that the above considerations, together with 
some of the suggestions regarding high tension line protection 
and wiring considered in Chap. XIY, cover the more important 
factors involved in the design of high tension lines for railway 
service. For further details of construction and for theoretical 
consideration of the limiting factors which enter into exception- 
ally high voltage installations reference should be made to the 
many complete works on these subjects. 

Estimates of construction costs on both distribution and trans- 
mission systems have been purposely omitted owing to the fact 
that the cost of copper is the dominating factor in these portions 
of the railway sj^stem and such cost is so variable a quantity that 
estimates or costs of previous installations have to be used with 
great caution when applying them to proposed systems. 



ii 



CHAPTER XVI 
POWER STATION LOCATION AND DESIGN 

Whereas the complete analysis of this subject would require a 
volume of generous dimensions, a few of the salient features to 
be borne in mind by the engineers in charge of the planning and 
construction of a complete electric railway system may well be 
suggested. 

Location. — The determination of the proper location for the 
power station from the one standpoint of most economical trans- 
mission of power to substations is made in a manner similar to 
that described for the location of substations, Chap. XIV, ex- 
cept that in this case the various loads are the full load ratings 
of the various substations supplied from the power station di- 
vided by the transmission line efficiency. The center of gravity 
of such loads spaced at the proper distance between substations 
locates the power station. 

With the power station, however, many other factors have 
to be considered before its location can be decided. The relative 
weight of these factors will vary with local conditions, but they are 
listed below in the order of importance as nearly as can be de- 
termined for the average case* 

The question of cheap coal supply to the steam power station 
is all important. In spite of this fact it is often neglected or 
given little thought, especially in the case of small stations, where 
it is often believed that coal may be drayed to the station at 
relatively small expense. The growth of traffic and competition 
with steam lines unwilling to cooperate with respect to the in- 
stallation of spur tracks or track connections with the interurban 
road have, in a number of instances, seriously embarrassed small 
interurban systems or at least prevented the power station reach- 
ing a reasonable cost of energy output. The station should be 
located on a railroad siding, or better, if the proposed line is in 
the vicinity of a navigable river, many of the other factors enter- 
ing into the location of the station may be waived in order to 
locate the station at a point where the coal may be deposited in 

162 



POWER STATION LOCATION AND DESIGN 163 

the bunkers directly from the coal barges. A notable example 
of such location is that of the proposed power station of the 
southern interurban line previously referred to, which is distant 
3 miles from the line of the road in order that it may be located 
where ocean going coal barges may be docked. 

The question of an adequate and reasonable soft water supply 
for boiler feed and condensing purposes should receive second 
consideration. In sections of the country where it is necessary 
to depend upon artesian well water for boiler feed it is either 
necessary to install rather expensive water softening plants or 
submit to a high maintenance and depreciation charge on boilers 
with considerable risk of service interruption. The marked loss 
of efficiency and corresponding increase in cost of generated 
powder if a condensing plant is occasionally forced to operate non- 
condensing is to be avoided if possible, especially in the case of 
steam turbines, whose principal advantage over the recipro- 
cating engines is the increased economy at high degrees of con- 
denser vacuum. Gravity intakes of pipe or concrete tunnel 
construction are preferable to long pipe suction lines, and con- 
siderable expense is warranted in bringing a generous supply of 
cold pure water into the cold wells of power stations and in pro- 
viding a free discharge of the hot well to waste under all conditions 
of water level in flood season and drought. Especially should 
the purity of condensing water be assm^ed with the surface type 
of condenser used to such an extent with steam turbines. 

Building foundations, especially for the heavy machinery of 
the station, should be unquestioned in their stability. Many 
instances may be quoted in which the saving of first costs of test 
borings or real estate was attempted at the later expense of the 
settling of foundations, carrying with it numberless construction 
and operating difficulties. Nor is it sufficient to determine the 
fact that there is good subsoil below^ a proposed station location. 
The depth of excavation necessary to reach this subsoil and the 
consequent cost of foundations should be carefully learned from 
preliminary test borings. 

The powder station often acts in the capacity of one of the sub- 
stations on the line supplying the high tension lines to other sub- 
stations not only, but transforming a portion of the generated 
electrical energy into a form adaptable to the nearby trolley 
and feeder system. This plan can only be carried out when 
the power station is located very near the right-of-way of the 



164 



ELECTRIC RAILWAY ENGINEERING 



railroad as the low voltage of the distribution system is not 
designed for transmission to any considerable distance. 

The cost of real estate is a very obvious factor in the determina- 
tion of power station site. With an interurban road the center 
of gravity of the load would naturally remove the station from 
the terminal cities where the cost of real estate is probably higher 
than at any other point on the line, but the operation of the line, 
or a portion of it at least, by the existing power companies of the 
terminal cities often involves power station additions or new 
locations where real estate is high in cost. This sometimes leads 
to the double-decking of stations with turbine rooms above the 






^^P-ilB 



iik.'~lK 



63.— Cos Cob power station of N. Y., N. H. & H. R. 



R. 



boilers. This construction has the further advantage of short 
connections between boilers and turbines. 

A feature often overlooked in the selection of a site is the con- 
venience of a location near the car house and shops. Such a 
location often prevents a duplication of shop equipment. The 
extent to which tools, supplies, and even labor may be used in 
common, especially in case of emergency, by both power station 
and car shops is surprising. Such cooperation between the 
departments of a large system must result in better service and 
improved economy of operation. 

Closely allied with the above is the necessity of locating the 
station at a point where employees and preferably some, if not all, 



POWER STATION LOCATION AND DESIGN 165 

of the heads of departments are willing to reside. Especially 
in the emergencies which are only too frequent in railway 
operation is this of great value to the company. 

Within the city limits the question of smoke nuisance sometimes 
has a bearing upon the problem, but as expert firing and special 
design of furnaces with the possible installation of smoke con- 
suming devices, if efficient ones can be obtained, reduce this 
trouble to an unobjectionable minimum, this factor has little 
weight in placing a station. 

Design. — The building which is to house the generating equip- 
ment should be designed for that purpose primarily, without 
too much thought for architectural beauty. Too many small 
roads have elaborate stations which are paying little or no re- 
turns on the investment and are found wanting in highly efficient 
equipment and attendance. Substantial brick or concrete 
buildings with generous basements for auxiliaries, piping, and 
wiring are necessary. They should be provided with plenty of 
head room for crane operation and generously lighted. Such a 
power station interior is illustrated in Fig. 63. This building 
is well constructed and planned to house the single-phase tur- 
bine generating equipment of the New York, New Haven & 
Hartford Railroad at Cos Cob, Ct. 

The costs of power station buildings cover a wide range, but 
for a fairly large modern station sufficiently commodious to ac- 
commodate all necessary machinery without overcrowding, a 
figure of from $3.25 to $3.50 per square foot of floor area 
should be allowed. 

The question of vibration and foundation construction should 
be given very careful attention, especially where high speed recip- 
rocating machinery is employed. Vibration has caused serious 
difficulties especially in turbine stations of the double-decked type 
with the turbines located on the second floor. Care should be 
taken also to plan for future extensions in the construction of 
the building, many stations being carried to the extreme of closing 
one end with temporary corrugated iron construction which may 
be readily torn down as extensions are made. 

Capacity. — In determining the total output of the station, 
methods similar to those used in the case of the substation are 
employed with due consideration given to the ''diversity factor." 
This factor, which has only recently been given its proper at- 
tention by operating companies, may be defined as the ratio of 



166 ELECTRIC RAILWAY ENGINEERING 

the summation of the maximum loads of the various substa- 
tions to the maximum load on the power station. That is to say, 
since the maximum loads come on the various substations at 
different times, the capacity of the power station may be con- 
siderably less than the sum of the substation capacities. The 
only accurate way, therefore, to determine the probable load on 
the power station is to plot the summation of all the substation 
load curves against the same abscissae of time and divide the 
average and maximum values of this load curve by the substa- 
tion and transmission line efficiency. Such a load curve will 
involve, aside from its momentary fluctuations, two or more 
well-defined peaks which must be taken into account in determin- 
ing the number of units to be installed. Reference to ^'sub- 
station design," Chap. XIV, will recall the method of subdivid- 
ing the total load into the proper number of generating units 
which is equally applicable to the power station, with the ex- 
ception that extensive subdivision into a relatively large number 
of small units involves more small duplicate auxiliary equip- 
ment in the case of the power station, incurring correspondingly 
increased maintenance and attendance charges. The generating 
equipment of the average interurban power station will not in- 
clude more than three units, one of which is often equal in capacity 
to the other two combined. 

The definition of 'load factor" found in Chap. XII is also 
applicable to power station design. The number and capacity 
of prime movers will depend upon both the load factor for 
each day and for the year. Efficient operation depends upon 
keeping well loaded all units which are operating. Low load 
factor means relatively large fluctuations of load from time to 
time. If the duration of the peak loads is sufficiently great 
and if their occurrence can be accurately predicted, an addi- 
tional unit or units may be started at the proper time to keep 
aH generators well loaded. If, however, the peak loads come on 
unexpectedly, as is often the case in interurban practice, suf- 
ficient equipment must be kept in operation continuously to 
carry the sudden loads. This involves low load factor upon any 
one unit, which is necessarily accompanied with low efficiency and 
relatively high operating cost. 

A low yearly load factor due to heavy traffic during certain 
seasons of the year involves high fixed charges on equipment 
which must lie idle for long periods. This is obviously a con- 



POWER STATIOX LOCATIOX AXD DESIGX 



167 



dition to be avoided as far as possible and is well illustrated bj^ 
the curves of Fig. 64 presented by H. G. Stott before the American 
Electric Railway Association in 1911. If a load factor of 15 
per cent, is assumed it is found that the fixed charges are more 
than double the operating charges. It is argued from this that 
it is often more economical to carry heavj' overloads upon 
equipment even at relatively low efficiency than to increase 

16 
15 

14 

13 

12 
11 
10 

K 9 

5^* o 



^5 
4 



1 

1 

54 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 

Per Cent Load Factor 

Fig. 64. — Factors entering total cost of power. 

the fixed charges bj- the installation of apparatus which is to be 
fully loaded at intervals only. 

Choice of Prime Movers. — AYhen the transmission of power 
from a nearby water privilege with its relatively low cost of energy 
is not possible, the following methods of clri\ing prime movers are 
usually open for consideration in laying out a new power station: 

1. Reciprocating steam engines. 

2. Steam turbines. 



1 


\ \ 1 








Mill 


1 






1 1 










1 1 


' 




i 1 i 












1 ! 








i i 1 


i 1 




1 1 1 


1 






! ! 1 


1 






i ! i 


\ i 








\ ' 




l\ M i . ^ 


i i 1 ! 1 ' ^ 




i 1 IJ 








1 


' \1 
















1 


i l\^° 


tan 


Fixe 


dC 


larg 


esp 


er K.W. 


H. 


1 


! i i\ 












1 


1 


^ 1 K 


. 1 1 






1 i 


i ^^ ^^ _.!__ 








! M ' • 1 






i 


■ 








1 1 


1 
























1 1 


1 


























JTo 


tal Operating k Maintenance Costs per K.W.hI 






,>^ 




1 1 








I ■ 


^1 ■ 






1 ' i ' 








/^ 
















1 1 1 


1 ' 1 


/ 
















1 ! 1 


t 1 i 



168 



ELECTRIC RAILWAY ENGINEERING 



3. Gas engines. 

4. Various combinations of the above. 

The relative advantages of the various prime movers and their 
combinations are best set forth by quoting Table XX published 
by Mr. H. G. Stott. In this table the various maintenance 
charges of each type of installation are not only given their proper 
weights, but the variation of the individual charges in changing 
from one prime mover to another are very clearly shown. In 
addition, the relative investments necessary for the various types 
of plant are compared with those for the reciprocating steam 
engine plant as 100 per cent. 

Table XX. ^ — Distribution of Maintenance and Operation Charges 
PER Kilowatt Hour 



Maintenance 



Recip. 

engines 



Steam 
turbines 



Eng. and Gas 
turbines I engines 



Gas en- 
gines and 
turbines 



Engine room, mechanical 

Boiler or producer room 

Coal and ash handling appara- 
tus 

Electrical apparatus 

Operation : 

Coal and ash handling labor.. . . 

Removal of ashes 

Dock rental 

Boiler room labor 

Boiler room oil, waste, etc 

Coal 

Water 

Engine room mechanical labor . . 

Lubrication 

Waste, etc 

Electrical labor 

Relative cost of maintenance 
and operation 

Relative investment in per cent. 



2.57 
4.61 

0.58 
1.12 

2.26 
1.06 
0.74 
7.15 
0.17 
61.30 
7.14 
6.71 
1.77 
0.30 
2.52 

100.00 
100.00 



0.51 
4.30 

0.54 
1.12 

2.11 
0.94 
0.74 



6 

0, 

57 

7, 
1 



0.35 
0.30 

2.52 

79.64 

82.50 



1.54 
3.52 

0.44 
1.12 

1.74 
0.80 
0.74 
5.46 
0.17 
46.87 
5.46 
4.03 
1.01 
0.30 
2.52 

75.72 
77.00 



2.57 
1.15 

0.29 
1.12 

1.13 
0.53 
0.74 
1.79 
0.17 
26.31 
3.57 
6.71 
1.77 
0.30 
2.52 

50.67 
100 . 00 



1.54 
1.95 

0.29 
1.12 

1.13 
0.53 
0.74 
3.03 
0.17 
25.77 
2.14 
4.03 
1.06 
0.30 
2.52 

46.32 
91.20 



Attention should be called to the fact that companies that have 
been operating railway power stations with reciprocating engines 
are realizing the marked economy which can be obtained by 
introducing low pressure turbines between the low pressure 
cylinders of the engines and condensers, and many such combina- 



1 Power Plant Economics by H. G. Stott, A. 1. E. E., 1906. 



POWER STATION LOCATION AND DESIGN 169 




170 



ELECTRIC RAILWAY ENGINEERING 



tion engine and turbine stations are now in operation. The 
output of a condensing engine may be increased from 20 to 25 
per cent, in this way with but Httle extra space occupied and 
often without building additions. 

The status of low pressure turbine development may perhaps 
be best judged from the summary of the report of the Committee 
on Power Generation of the American Electric Railway Associa- 
tion in 1910, which is quoted below as follows: 

''In general, the installation of low pressure turbines may be 
recommended wherever there are good engines installed, or in 
the case of a new installation where the load factor and the coal 
cost are high. In plants having a large installation of a good 
type of reciprocating engine the low pressure turbine may be 
added at a total cost, including new condenser, auxiliaries, 
foundations, piping, etc., of not to exceed $25.00 per kilowatt, 
thus bringing down the average overall investment per kilowatt 
of the entire plant and so reducing the fixed charges per kilowatt 
hour." 

In deciding whether steam turbines or engines shall be installed 
the question of steam economy naturally receives first considera- 
tion. While comparative tests under exactly similar conditions 
have probably never been made and although it is necessary to 
make some assumptions in order to compare fairly the test 
results where operating conditions vary slightly, the following 
table from Kent's Mechanical Engineer's Handbook will prob- 

Table XXI. — Comparative Steam Economy of Turbine and Com- 
pound Engine 



Per^cent. full load 


u 


75 


100 


125 


Avg. 85 
per cent. 


Pounds water per brake horse power 


600 hp. turbine 


13.62 

13.78 


13.91 
13.44 


14.48 
13.66 


16.05 
17.36 


14.51 


850 hp. compound engine 


14.56 



ably compare the two units with regard to economy as well as 
any. These values refer to a 600 hp. horizontal turbine oper- 
ating with saturated steam at 150 lb. pressure and 28 in. vacuum 
and an 850 hp. compound engine. These sizes of units are such 
as are often found in interurban power stations. 

A study of this table as well as other tests under nearly identical 



POWER STATION LOCATION AND DESIGN 171 

conditions indicates that there is httle choice between the two 
units from the standpoint of economy alone. 

The turbine seems to be the unit most often selected at the 
present time, however, probably because of its advantages over 
the compound engine with regard to first cost, space occupied, 
uniform rotation, freedom from vibration, low cost of founda- 
tions, etc. 

Steam Turbine. — If the steam turbine be decided upon the 
following items should be given particular attention in writing 
the specifications, in addition to the usual requirements of work- 
manship, grade of raw material, shipment, etc. Values will be 
substituted for a particular 1500 kw. specification in order that 
the requirements may be of more value for reference. 

Rating, 1500 kw., 2300 volts, three-phase, 60 cycles. 

Multistage, condensing. 

Steam pressure, 150 lb. 

Back pressure, 2 in. referred to barometric pressure of 

30 in. at 32°F. 

Superheat, 100°F. 

Excitation, 125 volts. 

Full load temperature rise at unity power factor, rated 

voltage, 40°C. corrected to room temperature of 25°C. 

Overload temperature rise, 125 per cent, load, rated 

voltage, unity power factor for 2 hours 55°C., corrected 

to room temperature of 25°C. 

Momentary overload of 100 per cent, at rated voltage and 

unity power factor without injury. , 

Economy expressed in pounds steam per kilowatt hour: 



Load per cent. 


Economy 


50 


20.7 


75 


18.9 


100 


18.0 


150 


19.0 



Speed regulation at end of heat run, speed rise when unity 
power factor full load is suddenly thrown off shall not 
exceed 4 per cent, of normal full load speed. When 
such load is gradually applied the speed variation shall 
not exceed 2 per cent, of normal full load speed. 
Voltage regulation at end of heat run when load is thrown 
off suddenly shall not exceed 188 volts. 
Insulation test shall be applied after heat run of 5000 



172 ELECTRIC RAILWAY ENGINEERING 

volts alternating current for 1 minute between armature 
coils and surrounding conducting material, and 1500 
volts alternating current for 1 minute between field 
winding and surrounding conducting material. 
A non-condensing run shall be made with rated load, 
power factor, voltage, steam pressure, and superheat 
against atmospheric pressure. 

Vibration. — ^The units shall operate smoothly and with- 
out undue vibration and noise under all conditions, and 
all revolving parts shall be accurately balanced. 
Centrifugal Stresses.- — ^The revolving field shall be suffi- 
ciently strong to resist for 1 minute without injury the 
centrifugal stresses produced by 20 per cent, excess 
of speed with armature and field circuits open. 
Steam Engine. — The features of particular importance in the 
steam engine specifications are found listed below, although these 
specifications do not refer to an engine for railway service. 

Type, horizontal, simple, side crank, designed to run 
"over." 

Non-condensing. 

Rating, 375 hp. at most economical cut-off, at specified 
steam pressure, back pressure, and normal speed. 
Service, left-hand direct connection to 250 kw., 2200 
volt, three-phase, revolving field alternator. 
Speed, 200 r.p.m. 

Steam pressure to be 1\25 lb. dry steam at throttle. 
Back pressure to be 10 lb. 
Superheat, none. 

Overload, 50 per cent, for 2 hours, momentary overload 
of 100 per cent, without injury. 

Economy expressed in pounds steam per indicated horse 
power hour. 

Speed regulation shall not exceed 1 J^ per cent, of normal 

speed when full load is suddenly thrown on or off. 

The engine shall be designed to operate in such a manner 

that the alternating current generator to which it is 

connected will operate successfully in parallel with other 

alternators of like general type. 

D. C. Generators. — The generating unit under consideration 

may be a portion of a turbo-generator or an engine driven 

machine. In a few instances in small cities direct current 



POWER STATION LOCATION AND DESIGN 173 

generators are still used, while in the larger urban systems and 
for practically all interurban stations alternating current energy 
is generated and transmitted to substations. The direct current 
necessary for distribution near the power station is usually 
converted from alternating current through the agency of motor 
generators or synchronous converters. The selection and in- 
stallation of this converting apparatus is made as indicated for 
the substation. 

If direct current generators are to be used, the engine type unit 
is to be preferred, especially in large capacities. Although fairly 
satisfactory direct current turbo-generators have been built 
and operated up to and including a capacity of 500 kw., in this 
country and 1500 kw. abroad, no great advance is anticipated 
in this direction. The commutator of a direct current generator 
using carbon brushes limits the speed to 1500 r.p.m. or less in 
large units. This is too high for good efficiency in generator 
design and too low for the best economy and lowest first cost in 
the turbine. In a few instances a high speed turbine has been 
geared to a low speed direct current generator with an overall 
cost and efficiency quite comparable with that of a Corliss 
engine and direct connected generator of like capacity. 

Direct current generators for railway service are necessarily 
of the overcompounded type, i.e., the series winding is so de- 
signed that the voltage at the power station bus bars is raised 
from 10 to 15 per cent, as the load comes on, to make up for the 
increased fall of potential on the distribution system. This 
compounding must be carefully specified for all generators in 
order that the load may be properly distributed between the 
various units of the station when operating in parallel. 

Many of the recent machines are of the interpole type, i.e., 
auxiliary poles are provided, with windings connected in series 
with the armature, located between the main field poles. These 
tend to neutraHze the effects of armature reaction sufficiently 
to improve commutation greatly. Since the capacity of the 
direct current generator is usually limited by its commutation, 
the size of unit necessary for a given output is materially re- 
duced if these poles are added. The ability of the generator 
to carry overloads is also materially increased where this design 
is adopted. 

In view of the importance of these questions of proper com- 
pounding and the use of the interpole design, care should be taken 



174 



ELECTRIC RAILWAY ENGINEERING 



to have the specifications very expHcit in this regard. The rela- 
tive costs, weights, and speeds of generators of ratings generally 
selected for such service are well indicated in Fig. 66 which has 
been reproduced from the American Handbook for Electrical 
Engineers. A 500 kw. d. c. low speed generator for railway 
service may be assumed to have an efficiency of approximately 
93 per cent, with the losses distributed as follows : friction, 2 per 
cent.; excitation, 1.6 per cent.; core loss, 1.4 per cent.; armature 
copper loss, 2 per cent. 

Polyphase A. C. Generators. — Generators supplying power to 
transmission lines and substations are now almost universally 
three-phase, regardless of the form in which the energy is supplied 
to the car or locomotive. The few exceptions are the single- 
phase roads supplied directly from single-phase generators 

35 70000 



30 60000 



25 50000 

20^ 400005 

^ I 

tn O 

15 1 30000"^ 

'o 
ft 

10 20000 



10000 



600 

500 

^.400 

rtsoo 

200 




















^ 








^ 


i^lPer 


^ 


^ 




^ 












v^ 




^^ 


" 














.°^ 


^ 
















>^ 


/- 

\ 
















/ 


/^ 


^■^>. 






Sui 


table g 


peed 


--_ 


100 








/ 





















100 



200 300 

Kw.Confinuous Rating 



400 



500 



Fig. 66. — Relative costs, weights and speeds of direct current generators. 



Even in these instances the generators are provided with three- 
phase star-connected windings of which but two are used. 

In many instances the transmission voltage is too high for 
generation without step-up transformers. In such cases the 
generating voltage is selected which may be secured at lowest 
cost. This is usually 2300, 6600 or 11,000 volts, as there is little 
gained in adopting 13,200 volts, the highest standard voltage for 
direct generation, unless this potential is available for trans- 
mission without transformers. 

It is not only unnecessary but inadvisable to specify too close 
regulation for alternators in railway service. That the regula- 



POWER STATION LOCATION AND DESIGN 175 

tion need not be close has been explained in connection with 
transmission line design. In addition to that fact, however, it 
will be remembered that if close regulation be not required, the 
reactance and armature reaction of the alternator may be greater. 
This tends to protect the machine under the heavy overloads and 
short circuits, to which it is likely to be subjected in railway 
service, by automatically lowering the voltage and thereby the 
short circuit current of the armature. Alternators of high arma- 
ture reaction also have the advantage of being able to keep in 
synchronism with one another more readily than those of better 
regulating qualities. This is another valuable feature in railway 
power station operation. 

AYith the turbo-alternator especially it is often impossible to 
make this protective reactance as high as desirable. Two 
methods are used to overcome this difficulty: One depends upon 
the automatic relays to connect auxiliary reactances into the 
feeder in case of overload or short circuit. The second and more 
desirable method introduces permanent reactances, in the form 
of coils of heavy cable wound upon non-magnetic cores, directly 
into the leads between generator and bus bars. This method 
has the advantage of protecting the generator against short 
circuits in the step-up transformers. As there are ordinarily no 
automatic switches or circuit breakers between generators and 
bus bars, these reactances form an excellent protection, particu- 
larly for very large units where the energy which may be supplied 
to a short circuit is very great. These reactances and their 
operation were described in detail by Messrs. Schuchardt and 
Schweitzer before the A. I. E. E. in 1911. 

The regulation of an alternator, to which previous reference 
has been made, is defined in the "Standardization Rules" of 
the A. I. E. E. as ''the rise in voltage (w^hen the specified load at 
specified power factor is thrown off) expressed in per cent, of 
normal rated load voltage." Although of less importance than 
in the case of lighting service, the regulation should be set forth 
in the specifications. 

Three methods of determining the regulation of alternators 
are listed in the above rules for 1914.^ These are briefly sum- 
marized below in their order of merit. 

^ See Standardization Rules of A. 1. E. E. Proceedings A. 1. E. E., 
August, 1914. 



176 ELECTRIC RAILWAY ENGINEERING 

1. Regulation determined from tests at specified load and power 
factor as compared with no load conditions. Both tests are of course 
run at constant speed and excitation. 

2. Regulation computed from test data of open circuit saturation 
curve and zero power factor saturation curve. 

3. Where it is impossible to obtain by test a saturation curve at zero 
power factor, comparison may often be made with tests at zero power 
factor on other machines of similar magnetic circuit. 

The regulation for the machine in question may then be closely pre- 
determined from open circuit and short circuit test curves. 

The full load regulation of polyphase alternators may be 
considered to vary from 5 to 18 per cent., depending upon design 
and power factor. 

The question of frequency is one to receive consideration in 
preparing specifications for alternators. The selection of the 
proper frequency for single-phase railway operation is discussed 
in detail in Chap. XXVII. For transmission to substations and 
conversion to direct current, however, a frequency of 25 cycles 
per second has become almost universal, although with recent 
improvements in interpole synchronous converters for 60 cycle 
supply there has been some tendency toward the use of the latter 
frequency. This is particularly true where lighting and railway 
supply are rather intimately connected. The poorer regulation 
with the higher frequency was pointed out in the discussion of the 
* 'Transmission System." This consideration, however, does not 
affect the problem of frequency determination as seriously as 
the unsatisfactory commutation of 60 cycle synchronous con- 
verters under the widely varying loads which are experienced 
in railway service. 

Having determined upon the frequency, the number of poles 
on the alternator is determined by the proper speed to be em- 
ployed for the particular type and size of prime mover selected. 
Speeds vary from 75 and 80 r.p.m. in large engine type generators 
to 3600 r.p.m. in turbo-generators. The corresponding varia- 
tion in the number of poles extends therefore from 40 in the first 
type to 2 poles in the high speed turbine generator. Although 
the question of the number of poles to be used is one of eco- 
nomical design, and therefore not necessarily included in the 
specifications, the latter should include very definite statements 
regarding frequency and type of prime mover to be adopted. 

The efficiency of the alternator should either be specified or 
the proposal should be required to include a statement of the 



POWER STATION LOCATION AND DESIGN 



111 



guaranteed efficiencies at varying non-inductive loads and at 
corresponding loads for at least one other specified power factor. 
Table XXII will indicate approximately the efficiencies and segre- 
gated losses to be expected from alternators of varying power 
capacity, although these values may be expected to vary con- 
siderably with frequency, voltage, speed, power factor, etc. 
Sixty cycle machines will, in general, have slightly higher effi- 
ciencies for a given rating than 25 cycle generators, while low 
voltage efficiencies may be assumed to be better than those of 
very high voltage alternators. 



Table XXII. — Efficiency and Losses, 


Usual Values^ 


Rating, 
kva. 


Efficiency, 
per cent. 


Friction, 
per cent. 


Excitation, 
per cent. 


Core, 
per cent. 


Armature 
copper and 
load losses, 

per cent. 


100 


91.0 


2.5 


2.5 


2.4 


1.6 


500 


94.0 


1.4 


1.5 


2.2 


1.2 


1,000 


95.0 


0.9 


0.9 


2.1 


1.0 


2,000 


96.0 


0.6 


0.7 


1.8 


0.9 


3,000 


96.5 


0.6 


0.6 


1.7 


0.8 


5,000 


97.0 


0.55 


0.4 


1.6 


0.5 


10,000 


97.2 


0.5 


0.35 


1.5 


0.45 



Although weights and costs of electrical equipment vary 
greatly with market conditions and individual designs, the curves 
of Fig. 67, obtained from the same source, will indicate these 
values sufficiently accurately for preliminary estimates. Weights 
and costs of 25 cycle generators will be from 10 to 20 per cent, 
greater than the values indicated in these curves. 

The ability of alternators to operate in synchronism with one 
another is particularly important in railway service. The effect 
of a high degree of armature reaction upon this quality in a 
generator has already been discussed. This feature may be 
further affected by the angular variation from a mean position 
of the revolving element of the alternator during different portions 
of the cycle. This is principally caused by angular variations 
in the prime mover due to acceleration and retardation during 
a single revolution. Since engine type units are obviously more 
seriously affected than turbines in this respect, it is well to limit 
the variation in alternators thus driven in preparing specifications. 
This variation has been defined by the A. I. E. E. as the ''maxi- 

^ American Handbook for Electrical Engineers. 
12 



178 



ELECTRIC RAILWAY ENGINEERING 



mum angular displacement, expressed in electrical degrees (1 
cycle = 360 deg.) of corresponding ordinates of the voltage 
wave and of a wave of absolutely constant frequency equal to the 
average frequency of the alternator or circuit in question." 

Rating. — The method of rating generators has been radically 
changed as a result of the new Standardization Rules of the A. I. 
E. E.^ These are based upon the actual temperatures of the 
supposedly hottest portion of the winding instead of the rise in 
temperature above that of the room as previously considered. 
The new method seems to be a great improvement for it is well 



1000 20 

900 18 

800 16 

700 14 

•600 ■»12 

^. ? 
»5500filO 

400 8 

300 6 

200 4 

100 2 



\ 


















^ 


^ 


\ 


\ 












^^ 


^ 








\ 


\ 






/ 


















\ 


^ 


4,. 


















/ 


/ 


^ 




fc^e>.. 












/ 


/ 








<^ 


JIa 










/ 




















/ 


/ 


















\ 


/ 




















/ 


V 


^ 






Suita 


bleR. 


^M. 








/ 























100000 



80000 



60000 



40000 



20000 



200 400 600 800 1000 1200 1400 1600 1800 2000 
Kv-a Eating 

Fig. 67. — Relative costs, weights, and speeds of alternating current 

generators. 

recognized that actual temperatures influence the physical con- 
dition and life of insulation rather than temperature rise above 
room conditions, especially when the latter may vary over a wide 
range. 

Without going into detail regarding these new methods of 
rating, it may be stated that three ways of determining tempera- 
tures are listed in order of preference. 

iSee A. I. E. E. Proceedings, August, 1914. 



POWER STATION LOCATION AND DESIGN 179 

1. Thermometer method. 

2. Resistance method. 

3. Embedded temperature detector method. 

The first two methods will be recognized as having been in 
common use in the past, although in the new rules a generous 
correction factor must be applied to account for the difference 
between hottest spot temperatures and those actually read. The 
third method is more elaborate and requires special provisions 
for temperature measurement when the generator is constructed. 
The correction factor is, however, of less magnitude than in the 
previous methods. 

Having determined the hottest spot temperatures at different 
loads the rating depends upon the excess of such temperature 
above the arbitrary and fixed ambient temperature of 40°C. 
With cotton, silk, paper and other fibrous materials, untreated, 
an excess of 55°C. is allowed, while this figure is increased to 
65°C. for similar materials which have been treated and to 85°C. 
for mica and asbestos. 

Generators for Single -phase Traction. — Distribution to single- 
phase railway systems is possible from three-phase generators 
by tapping the phases consecutively into adjoining sections of 
trolley. It is, however, difficult to maintain a balance upon such 
a system and the switching and cable layout are somewhat com- 
plicated. There is, therefore, some demand for single-phase 
generators but since the entire periphery of the armature in a 
generator designed as such cannot be used to good advantage, 
a three-phase machine connected ' 'Y" is usually adopted. Two 
of the coils of the winding are used for the single-phase supply 
while the third coil is kept for emergency demands or to supply, 
in connection with the other two coils, any demands that may 
exist for three-phase power in the station. As the output of the 
generator is reduced in this manner to about two-thirds of its 
rating as a three-phase generator and as the single-phase railway 
system must necessarily operate at a considerably lower power 
factor than a direct current system supplied from three-phase 
substations, great care must be exercised in specifying the proper 
rating for generators to be used under such conditions. 

Transformers. — The step-up transformers in the power station 
are identical except in size with those discussed in detail in Chap. 
XIV, the low tension winding becoming the primary in this case. 
As in the case of the substation if the transmission line voltage 



180 ELECTRIC RAILWAY ENGINEERING 

does not exceed 13,000 volts, the generator armatures may be 
wound for full voltage and the transformers omitted. 

Transformer specifications should include the rating, fre- 
quency, primary and secondary voltages, type, i.e., whether oil, 
air, or water cooled, hottest spot temperature on full load and 
overloads, efficiency, power factor of load, insulation test, regu- 
lation, etc. Such transformers as would be used in power station 
service might be expected to have a regulation of 1.2 per cent., 
a full load efficiency of 98 per cent, or slightly more, and with- 
stand a 10,000 volt insulation test for a 2200 volt rating. 

Rapid advancement has been made during the last few years 
in the size and voltage of power station transformers. The 
three-phase transformer, combining all three phases in a single 
tank, is now coming into rather general use in this country. 
This practice has been in vogue abroad for some time. Trans- 
formers of 10,000 kv.a. rating for three-phase voltages as high 
as 120 kilo volts are not at all uncommon and in spite of the 
previous feeling that extra high voltages must be supplied from 
''Y" connected transformers, several delta connected trans- 
formers have been installed at the highest operating voltages yet 
placed in service. 

Switchboard. — This portion of the power station equipment 
is not materially different from that described in connection with 
substation design and that portion which may be installed to 
control substation apparatus in the power station is, of course,^ 
identical therewith. 

Above 13,000 volts and often below that voltage the board is 
of the remote control type with switches and usually cables, bus 
bars and transformers as well, located in fire-proof brick or con- 
crete cells. No protective device is installed between the gener- 
ators and the bus bars, although the out-going transmission lines 
are protected with time limit relays, lightning arresters, and 
choke coils. For the purpose of synchronizing generators and 
in order to balance the loads properly between the various 
machines operating in parallel, the generator panels are often 
equipped with auxiliary circuit (125 volt) control devices for 
regulating the governors and thereby the speed of the prime 
movers. 

Exciters. — Although the individual alternators are occasion- 
ally provided with separate belt-driven or direct connected ex- 
citers especially in small installations, it is customary to provide 



POWER STATION LOCATION AND DESIGN 



181 



a steam-driven and usually a motor-driven exciter set, the former 
being necessary in starting a plant. As a considerable amount 
of 125 volt direct current power is used about the station for 
auxiliary control circuits, etc., the exciters should be considerably 




If^ZiT 



Fig. 68. — Sectional elevation of typical high-voltage switch house. 

larger than the combined demands of all alternator iSelds which 
they are called upon to supply. In selecting the exciter capacity 
it should also be borne in mind that the generators at low power 
factor require considerably increased excitation to maintain 



182 



ELECTRIC RAILWAY ENGINEERING 



normal voltage at full load and the exciter should, therefore, be 
sufficiently large to supply this demand. As an additional pro- 
tection against failure of excitation current which is the back bone 




9PTS aaonpojd: 

of the power plant, storage batteries are often '^floated" on the 
125 volt bus bars, ready to supply energy to the field windings 
in case of failure of the exciters. 



POWER STATION LOCATION AND DESIGN 



183 



Arrangement of Equipment. — The most convenient arrange- 
ment of apparatus and wiring in a power station is greatly influ- 
enced by local conditions. A good idea of such arrangement may 
be obtained from Fig. 65 which represents a transverse section 
through the boiler and engine room of a typical power station 
using reciprocating engines direct connected to alternators, water- 
tube boilers, and jet condensers. A similar section through the 
high tension switch house is shown in Fig. 68. A plan view 
of a gas engine station will be found in Fig. 69, while Fig. 70 
shows a section of the turbine station of the Indianapolis and 
Cincinnati Railway Company at Rushville, Indiana. 

Cost of Power Station Equipped. — Complete power stations 
including buildings, but not cost of land, may be estimated to cost 
between $85 and $150 per kilowatt of rated output, depending 
upon the elaborateness of design and the addition of mechanical 
labor saving and safety devices. Occasionally the above mini- 
mum figure may be greatly reduced, as was the case of the rather 
unique double-decked station of the Fort Wayne and Northern 
Indiana Railway Company, Fig. 71, located in Fort Wayne, 
Indiana, whose detailed costs listed in Table XXIII are taken 



Table XXlll. — Cost of Completed Power Station. 8500 Kw. No 
Substation Apparatus 




Total cost Cost per kw. 


Building: Including general concrete and steel 
work, galleries, coal bunker, smoke flue, con- 
denser pit, coal-storage pit, etc 


$93,217 

259,711 

118,313 

33,790 

7,990 

50,500 


$10.97 


Generating Plant : Including turbine, generators, 
exciters, cables, switchboard, transformers, 
and ventilating ducts 


30 55 


Boiler Plant: Including boilers, superheaters, 
stokers, piping, pumps, heaters, settings, 
breechings, and tank 


13.92 


Condenser Plant: Including condensers, pumps, 
free exhaust, water tunnels, and intake screen. 

Coal Handling Plant: Including gantry crane, 
crusher, motors, and track 


3.98 
0.94 


Erection, superintendence, engineering, and 
miscellaneous . . . 


5 94 








$563,520 


$66.25 



184 



ELECTRIC RAILWAY ENGINEERING 




POWER STATION LOCATION AND DESIGN 



185 



from a paper before the American Street and Interurban Railway 
Association (now American Electric Railway Association) by 
Mr. J. R. Bibbins. 

In contrast to the above double-decked station there ma}' be 
found listed below the final estimate exclusive of land for a 
modern interurban power station in the south of 2000 kw. 
rated capacity involving substation equipment of 300 kw. 



EeinforceJ CiuJer Concrete 




Fig. 71. — Sectional elevation of typical double-decked turbine 
power station. 

capacity. This estimate is given in considerable detail as it is 
believed it wiU be of value in determining the relative costs of the 
various portions of the equipment, even if the actual prices do 
vary, as they must from time to time. While the cost has been 
reduced to a kilowatt basis it should be stated that the estimates 
are from detailed figures based upon actual quotations, the 
values per kilowatt being results of the estimate and not the basis 
thereof. 



.86 



ELECTRIC RAILWAY ENGINEERING 



Table XXIV. — Estimate for Complete Interurban Power Station 
2000 Kw. Rating with 300 Kw. Substation Equipment 



Total cost 



Cost per kw. 



Surveying and clearing site 

Excavating and grading 10,000 yd. @, 25 
cts . 



Building proper, 12,000 sq. ft. @ $3.25. . . 
Machinery foundations, 2 turbine founda- 
tions, 100 yd. @ $10 

1 Stack foundation, 200 yd. @ $8 

2400 hp. boiler foundation, @ 1.60 hp. . 

2400 hp. boiler settings @ 2.60 hp 

Miscellaneous foundations, 100 yd. @ 10 

Stacks and flues, 1 stack 9 ft. X 180 ft. 

(Custodis) 

2400 hp. flues @ 1.00 hp 

Dampers, regulators, etc 



Coal and ash handling apparatus, locomo- 
tive crane 

Conveyor, crusher and scales 

Ash cars and track 

Ash pit 

Storage yard tracks, etc 

Conveyor trestle 



Cranes, lighting, plumbing, etc., crane. 

Lighting 

Plumbing 

Gratings, railings, etc 



Wells, intakes, etc 

Boilers, stokers, etc., boilers, 2400 hp. 

15.50 erected 

Stokers, 2400 hp. @ 5.00 erected. . . 



Piping, valves, etc 

Steam turbines, Curtiss turbines 2-1000 kw, 
Freight and starting 



$300 



2,500 



1,000 
1,600 
3,850 
6,250 
1,000 



8,000 
2,400 
1,000 



9,000 
7,500 
600 
500 
1,500 
1,000 

5,000 
1,500 
1,000 
1,000 



37,200 
12,000 



60,000 
3,000 



2,800 
39,000 



13,700 



11,400 



20,100 

8,500 
20,000 

49,200 
23,000 
63,000 



1.40 
19.50 



6.85 



5.70 



10.05 

4.25 
10.00 

24.60 
11.50 
31.50 



POWER STATION LOCATION AND DESIGN 



187 



Estimate for Complete Interurban Power Station 2000 Kw. Rating 
WITH 300 Kw. Substation Equipment. — Continued 



Total cost Cost per kw. 



Auxiliaries, heater, 1800 hp, 
Condensers, 2 @ $5500 . . . 
Feed pumps, 2 @ 1100. . . 

Fire pump, 1 @ 1100 

Oiling system 

Freight and erection 



Generators, exciters, rotaries, etc., rotary 

converter, 300 kw. @ $16.00 

Transformers, 480 kw. @ 10.00 

Turbine exciters, 2-35 kw 

Motor-generator set, Itg. 100 kw. @ 40 . 
Freight and erection 



Switchboards and wiring, 16 panels. 

3 blank panels 

Miscellaneous brackets, etc 

Freight and erection 

Wiring @ $1,50 per kw 

Switch cells 



Miscellaneous 

Sundry supplies and expenses. 



Grand total exclusive of land and engineer- 
ing salaries and commissions. 



900 
11,000 
2,200 
1,100 
1,500 
2,000 



4,800 
4,800 
3,600 
4,000 
2,000 

7,900 
150 
150 
1,000 
3,000 
1,000 



18,700 



19,200 



13,200 

2,500 
2,500 



$304,300 



9.35 



9.60 



6.60 

1.25 
1.25 



$152.00 



CHAPTER XVII • ' 

BONDS AND BONDING 

The circuit which suppHes current from the substation to the 
car has already been outHned. The return portion of this circuit 
is made up of the track rails, being augmented by return copper 
feeders in parallel with the track only in cases of heaviest service. 
As rail lengths of either 30 or 60 ft. are used, a single rail will have 
•88 or 176 joints per mile at which the electrical resistance of the 
connection between rails made by means of corroded fish plates 
would normally be very high. With this high resistance directly 
in series with the return circuit, any reasonable addition to the 
copper in the positive feeders is of little value. It was quickly 
found, therefore, in the operation of the early railway systems 
that the ends of rails must be connected electrically by conductors 
of lower resistance than the fish plates. These conductors have 
been designated as ''bonds." 

In the first installations bare copper negative return wires were 
laid along the ties between the rails and connected with the center 
of each length of rail with a copper wire. This method, however, 
proved very expensive and was abandoned, although it has been 
reinstated recently of necessity in similar form where traffic is 
very heavy, particularly in city systems. Later the ends of rails 
were bonded by means of No. 6 galvanized wire bonds clamped 
under the heads of track bolts. Such bonds were not only soon 
destroyed by galvanic action in the earth but were found to be of 
such high resistance as to be of little use. A slight decrease in 
the contact resistance of these bonds was later affected by forcing 
the bond wires into holes drilled in the heads of the bolts. The 
inability to reduce the track resistance sufficiently by any of the 
above means led to the introduction of the solid copper bond 
which in turn developed into the laminated strip copper and 
stranded copper bonds which are preferable because of their 
flexibility. 

Several distinctive types of the latter bonds have how come into 
very general use and a brief description of each will therefore be 
found below. 

188 



BONDS AND BONDING 189 

Compressed Terminal Bonds. — This type of terminal has 
been applied to various designs of copper bonds. It consists of a 
cylindrical head varying from ^^ in. to 1 in. in diameter and 
slightly longer than the thickness of the web of the rail. This 
head is forced into a recently reamed hole in the web of the rail 
by means of a heavy screw clamp provided with a conical contact 
which engages the center of the bond head and causes it to ex- 
pand and flow under the pressure applied so that it makes inti- 
mate contact with the inner surface of the hole and heads over, 
rivet like, so as to prevent easy loosening or removal. Some 
compressed terminal bonds have their heads drilled with an axial 
hole through which a tapered steel pin is driven in order to expand 
the copper head well into the hole in the web. 

Compressed terminal bonds may be installed so as to surround 
the fish plate or they may be of the ' 'protected" type, installed 
before the fish plates are put on and later covered by the latter 
plates, thus protecting the bond from mechanical injury or theft. 
When installing this bond great care must be exercised not to 
drill the holes much before the bonds are inserted and to use a 
lubricant when drilling holes which will not produce an insulating 
film on the inside surface of the hole. Clear water or a solution 
of bicarbonate of soda and water may be used but oil and soapy 
water should not be tolerated as lubricants. 

Soldered or Brazed Bonds. — Bonds similar to the above but 
with flat tinned heads are sometimes soldered or brazed to the 
side of the rail head or under the rail flange by means of a gasoline 
or oxy-hydrogen blow-torch after the rail has been brightened at 
the point of contact. These bonds have not proved entirely 
satisfactory, however, as they are quite likely to work loose and 
are also quite easily stolen. 

Electrically Welded Bonds. — A process of electrically welding 
a short laminated copper bond, provided with a brass head, upon 
the sides of the. rail heads has recently been developed. This is 
accomplished by the use of a very large alternating current pass- 
ing through the very small areas of bond, rail head, and carbon 
terminal in series and thus bringing the two metals to a welding 
heat. While this process is termed welding it is more correctly 
brazing, since two different metals are joined with a flux of 
borax between. The large alternating current necessary is pro- 
duced by making the yoke and jaws which grip the bond and rail 
head a part of the secondary circuit of a current transformer whose 



190 



ELECTRIC RAILWAY ENGINEERING 



primary is supplied from the alternating current side of an in- 
verted synchronous converter. This converter is mounted on the 
car which carries the bonding outfit and is supplied with direct 
current from the trolley. The ratio of transformation and 
impedance of the transformer secondary circuit are such that the 
current flowing through the weld is in the neighborhood of 1000 
amp. The particular equipment from which these values were 
obtained, Fig. 72, involves a 15 kw. transformer supplied from 
an 18 kw. inverted synchronous converter operating at a fre- 
quency of 25 cycles. The transformer was connected for two 




Fig. 72. — Apparatus for electrically welding bonds. 

voltages of 375 and 500 volts respectively, while the secondary 
voltage varied from 1 to 7 volts. The converter was also used 
as a motor to propel the car. 

In this particular test^ with the 500 volt connection, the time 
required to make a weld averaged 82 sec. with an input to the 
car per bond of 797 watt hours. An estimate of the cost of 
electric welding, assuming that 40 welds per day can be made, 
would, therefore, result as follows, if power costs 2.5 cts. per 
kilowatt hour at the car: 

1 Thesis, Purdue University, 1910, by Broadwell, Cole and Stevenson. 



BONDS AND BONDING 191 

Table XXV. — Cost of Electric Welding 

Cost of energy 0.797 X 0.025 $0 . 019 

Cost of bond 0.30 

Cost of labor . 112 

Sundries 0.01 



$0,441 



This estimate is slightly low since it is always necessary to grind 
a bright place on the head of the rail before the bond is applied. 
This is accomplished by means of an electric motor-driven grinder 
connected with the trolley. The power for this purpose was not 
included in the above estimate, although a labor item was allowed 
to cover the work. It is safe to say, however, that these bonds 
may be installed for 45 cts. each while the other types vary from 
something less than this up to 70 cts. each installed. 

Amalgam Bonds. — Bonds consisting of semiplastic amalgam 
forced between the brightened surfaces of rail web and fish plate 
are occasionally found, although not in common use. 

Aside from the above, several methods of making continuous 
rail joints of high electrical conductivity may well be classified 
under the heading of bonds. Such methods in common use are 
as follows: 

Cast Welded Joint. — In making this joint, melted iron of 
special composition and high conductivity is poured around the 
rail ends, with the exception of the heads, while they are enclosed 
in a sand or iron mould of such shape as to leave a heavy lug of 
cast iron about the ends of the rail. While it is rather difficult 
with this process to raise the temperature of the rail quickly 
enough to insure molecular adhesion between the rail and the 
molten metal, yet very satisfactory results have been obtained in 
many instances from both the standpoints of electrical conduc- 
tivity and mechanical rigidity. 

Thermit Welded Joint. — A combined joint and bond of com- 
paratively recent origin is produced by the ''thermit" process. 
As in the previous method, a mould of sand is made about the 
rail ends, but in this case only sufficient thermit for one joint is 
melted at a time. This melting is accomplished by making use 
of the well-known fact that finely divided aluminum when 
oxidized develops a great amount of heat. This reaction has 
been recently brought under control so that a small amount of 
powdered aluminum mixed with iron oxide, if ignited with a 



192 



ELECTRIC RAILWAY ENGINEERING 



small amount of ignition mixture, will react as above explained 
with sufficient heat to melt the iron which in turn is poured about 
the rail ends. This produces a joint similar to the cast weld 
with less metal but with apparently quite as good electrical and 
mechanical characteristics. 

Electric Welded Joint. — In contrast to the electric welded 
bond mentioned above there may be found in the city tracks of 
many railway companies the electric welded rail joint. This, a 
rigid rail joint produced by electrically welding heavy iron bars 



Voltmeter 




Transformer 



Ac. Side Rotary 

> 




Dc. Side Rotary 



Ammeter 



^ro 




Voltmeter 



' Special Current 
Transformer 




+ 



O 



\ 



Connected to Bond Clamps 



Fig. 73. — Connections for electric welding of bonds. 



on either side of the webs of adjacent rail ends, should be carefully 
differentiated from the electric welded bond, although the proc- 
ess of welding is almost identical with that outlined above, with 
the exception that iron only is used and the size of weld and corre- 
sponding power used are much greater. In this latter type of 
joint, iron filler blocks are inserted between the rail ends and 
ground to the form of the rail head so that the joint is entirely 
closed and the operation of cars over rail joints is made so much 
the smoother. This joint has given very satisfactory service both 
electrically as a bond, for its conductivity is practically equal to 



BONDS AND BONDING 193 

that of the rail, and mechanically as a rail joint, the breakages 
not exceeding 1 per cent, of the total joints welded after several 
years of service in at least one installation and averaging very 
close to this record on several other roads. 

AVhen considering any of these three methods of making combi- 
nation rail joints and bonds where the joint is necessarily mechan- 
ically rigid, it should be borne in mind that the track will expand 
in hot weather sufficiently to throw it noticeably out of gauge 
if it is not rigidly held in place bj^ street paving. None of these 
methods are therefore suitable for anything but paved city 
streets, unless an exception be made of the few cases where they 
have been tried with expansion joints every few hundred feet. 
At these joints of course some other type of bond must necessarily 
be installed. 

As these processes combine a rail joint with a bond, doing away 
with fish plates, track bolts, and other types of bonds, their 
expense is naturally much greater than that of any other bond 
alone. Herrick and Boynton^ give average prices for these 
combined joints of from S2.67 each for cast wielded joints and 
$4.50 each for the 'Hhermit" process, up to $5.50 or $6.00 per 
joint for the electric weld. These figures do not include opening 
and closing the pavement around the joint in case old track is 
being treated, which cost will vary from $1.00 to $1.25 per joint. 

Bond Testing. — The bond resistance of a well bonded track 
using 4/0 B. & S. bonds will range from 5 to 7 per cent, of the 
resistance of the track return. With a few missing bonds or 
with poor contacts between bonds and rails this resistance may 
be increased many times. While the maximum allowable vol- 
tage drop in the return circuit is often ver}^ rigidly fixed in the 
city systems by municipal ordinance, it is for the interest of the 
operating company to keep this resistance at a minimum value, 
since the voltage at the car varies inversely and the losses vary 
directly with the resistance. It has been customary, therefore, to 
make frequent tests for the resistance of rail bonds and the stand- 
ard has been rather arbitrarily set that the resistance of a bond 
shall be less than that of 3 ft. of rail. 

The comparison of the resistance of the bond with that of 3 ft. 
of rail may be very readily made by making use of the current 
flowing in the rail. Two contacts, (a) and (b) Fig. 74, consisting 
of hardened steel knife edges or points connected to a milli- 

^ "American Electric Railway Practice," by Herrick and Boynton. 

13 



194 ELECTRIC RAILWAY ENGINEERING 

voltmeter (V), are applied to the head of the rail at a distance 
apart corresponding to the length of the bond. A third contact 
(c) is permanently spaced 3 ft. distant from one of the former 
contacts, (6). If another milli-voltmeter (V) be connected 
between (6) and (c) and read simultaneously with the meter 
connected to (a) and (h), the readings are proportional to the 
resistance of a 3 ft. section of rail and that of the bond re- 
spectively. The bond may be pronounced in satisfactory con- 
dition if 

7 < r (103) 

while if (F) be too great its departure from the required value 
may be recorded as 

^-yj — — per cent. (104) 

Care must be exercised in making these tests not to damage 
the milli-voltmeter by attempting to measure an open bond. 



<r> 



Fig. 74. — Connections of bond testing meters. 

It is always well to try the bond on a meter with a 15 volt scale 
first and if the drop in potential is found to be within the range 
of the milli-voltmeter to make the final reading with the latter 
instrument. 

As this process is a rather slow and tedious one where there 
are a large number of bonds to be tested, various methods have 
been devised for making the tests on a car as the latter is traveling 
over the road. Usually this is necessarily done when the regular 
cars are off the line at night or with very little varying current in 
the rails. The current sufficient to determine the voltage drop 
in rail sections and bonds is fed through the local rail section by 
means of specially designed trucks, the current being controlled 
by a rheostat on the test car.^ 

If it be desired to learn only the total resistance of the track 
return, this may be determined after the cars are off a section of 
line by passing a measured current through the rails by means of 

^"Practical Electric Railway Handbook," by Herrick. 



BONDS AND BONDING 195 

a feeder to the distant end of the Une and a rheostat at that point 
in series therewith. A second feeder may be disconnected from 
the generator temporarily and used as a potential lead so that the 
fall in potential in the track may be read upon a voltmeter in the 
power station. 

Cross Bonding. — Thus far the bonding of rail ends alone has 
been considered. It is sometimes necessary to provide against 
the greatly increased resistance of the return circuit due to a 
possible open- bond by connecting the rails together electrically 
by means of cross bonds spaced several hundred feet apart. 
These usually consist of bare copper wire of approximately the 
size of the bonds soldered to the bonds on opposite rails or to 
special single-headed bond terminals forced into the rail web. 
Thus if a bond be open, the return current on that particular 
rail would follow the nearest cross bond to the other rail and find 
its way back to the original rail at the next cross bond nearest the 
power station. 

As the bonding of all joints in special track work such as 
switches, cross-overs, and frogs would often involve a large 
number of bonds, a heavy cable is often laid around such portions 
of the track and thoroughly bonded to the sections of track on 
either side thereof. 



CHAPTER XVIII 
ELECTROLYSIS 

The subject of the electrolysis of underground pipe systems is 
closely allied to that of bonding. Beginning with the rather 
general introduction of the direct current street railway systems 
in the early nineties, with their track return and relatively poor 
bonding, and extending through the rapid development and 
improvement of such systems, the question of electrolysis, its 
cause and prevention has maintained an important place in the 
discussions of the engineers of gas and water works corporations 
as well as the telephone and street railway interests. 

It has, of course, been known for a long time that if a direct 
current be allowed to flow from a metal electrode, through an 
electrolyte to a second metal electrode, a chemical reaction takes 
place at the expense of the positive plate, i.e., this plate is actually 
eaten away, the metal removed therefrom forming a salt with 
some of the acid radicals of the electrolyte. During these reac- 
tions which take place similarly when moist earth is the electro- 
lyte it was noticed that hydrogen was given off at the cathode or 
negative terminal while oxygen was liberated at the anode." It 
was supposed for some time that those free gases were formed 
from the decomposition of the water in the earth. When it was 
later found, however, that this action often took place with poten- 
tials between terminals of the order of hundredths and even 
thousandths of a volt, which are not sufficient to decompose water 
and free these gases at their respective electrodes, a further 
study of the problem was undertaken. 

Experiments carried on at the University of Wisconsin and 
recorded in the discussion of a very able paper upon this subject 
presented before the American Institute of Electrical Engineers 
by the late Isaiah H. Farnham in 1894 demonstrated the fact that 
with iron electrodes embedded in moist earth electrochemical 
action is substantially as follows : Most earths contain salts of 
alkaline metals. Merely a directive electromotive force of the 
order of 0.001 volt will cause the acid radical of these salts to be 

196 



ELECTROLYSIS 



197 



isolated. This radical then attacks the anode. Suppose sodium 
sulphate (NaSOj be present in the earth; this is broken up by 
the current into (Na) and (SO4). The SO4 forms with the posi- 
tive iron electrode (FeS04) while the hydroxide of sodium 
(NaOH) is formed at the cathode. When the earth in the neigh- 
borhood of the terminals becomes saturated with these com- 
pounds they diffuse toward one another and finally meet in the 
earth at a point easily detected by the formation of a green 
precipitate of ferrous hydroxide, and the original salt. This 
reaction causes a local rise in temperature at the point where the 
precipitate forms. The reactions mentioned above, which take 
place at the electrodes, release oxygen gas at the anode and 
hydrogen at the cathode, the former resulting from an excess of 
SO 4 forming an acid with the hydrogen of the water and setting 




Pipe or Lead Cable 
Fig. 75. — Direction of current with negative trolley. 



oxygen free. The latter is the result of the formation of the 
hydroxide of sodium with water, the free atom of hydrogen 
from the water being liberated. 

The one point of practical interest in this series of reactions is 
the fact that iron is removed from the positive electrode to make 
ferrous sulphate and later ferrous hydroxide, and the size and 
weight of this plate are reduced thereby. This loss of metal 
from the buried plate is proportional to the current flowing there- 
from. Now if the track return circuit be of high resistance, a por- 
tion of the return current will flow back toward the power station 
on underground pipes and cable sheaths, leaving these conductors 
at points near the power station to complete the circuit through 
the earth or on the rails and negative cables to the switchboard. 

Since the above chemical reactions take place in the case of 



198 



ELECTRIC RAILWAY ENGINEERING 



electric railway currents leaving water and gas mains and the 
sheaths of telephone cables and entering the earth with values 
ranging from an infinitesimal leakage up to several hundred 
amperes in extreme cases, the importance of the study of the mag- 
nitude of troubles from electrolysis and the remedies to be applied 
is at once apparent. 

In the early days of electric traction the bonding of the track 
and the proper installation of a low resistance return circuit were 
seriously neglected, as has been explained in the previous chapter. 
It was also customary at first to connect the negative terminal 
of the generator with the trolley and the positive to the rail in 




EAST 
BOSTON 



Fig. 76. — Early map of electrolysis in Boston. 



many installations, this being just the reverse of the present 
method. These two conditions tended, first, to force a relatively 
large proportion of the current to follow the pipe and cable sys- 
tems in place of the track and, secondly, to make such pipe and 
cable systems positive to the rail over a wide area of territory in 
the average city. 

This condition is clearly shown in the accompanying Fig. 75, 
which shows the direction of earth currents, and Fig. 76, repre- 
senting the conditions in Boston, Mass., when the question of 
danger from electrolysis was first seriously considered. At the 
time this map was plotted from a large number of tests made of 



ELECTROLYSIS 



199 



the voltage between pipe systems and rails, the trolley was negative 
and the rails positive. The shaded area designated as the '' danger 
area" represents the territory in which the pipe systems are 
positive to the rails and therefore in which electrolysis might be 
expected to take place. The large extent of this danger area 
implies a great amount of possible trouble from electroh^sis and 
a considerable expenditure of time and money for the proper 
maintenance of tests and the location of serious leakages of 
current. 

A marked advance w^as soon made, however, in this problem 
when the trolley was connected with the positive terminal of the 
generator and the rails with the negative terminal as in Fig. 77. 
This change would naturally limit the danger zone to a compara- 



+ 



^ 




D~ 00000 



I 




Fig. 77.- 



Pipe or Lead Cable 
-Direction of current with positive trolley 



tively small area near the power station where the current which 
returned on the various pipe lines would leave these conductors 
and pass through the earth to the rails or return conductors and 
thence to the negative terminal of the generator. The effect of 
such a reversal of trolley polarity is obvious in Fig. 78 which 
represents a potential map of the territory included in Fig. 76 
taken after the trolley of the West End system of Boston was 
made positive. This limitation of the area in which electrolysis 
may take place woujd usually increase the current leaving the 
pipes at any one place. 

In this connection it might be of interest to note some of the 
results of electrolysis with currents of different magnitudes. 
Experiments have proved that 1 amp. flowing steadily from 
an iron surface will remove approximately 20 lb. of iron in 1 



200 



ELECTRIC RAILWAY ENGINEERING 



year, while the same current flowing continuously from a lead 
cable sheath or pipe will eat away 75 lb. of lead in the same time. 
A 48 in. iron water main in Boston was pitted in various places 
to a depth of %6 in. in from 4 to 5 years, the average potential 
between pipe and rails being 8 volts with a current flowing in the 
pipe ranging from 5 to 95 amp. In this case the pipe was about 
23-^ ft. below the rails of the street railway company. 

Nor is the trouble confined alone to the points where the 
current leaves the pipe for other conductors. The joints in' pipe 
lines often have relatively high resistance as compared with the 
pipe itself and even when compared with the surrounding earth 




EAST 
BOSTON 



Fig. 78. — ^Later map of electrolysis in Boston 



in some instances. This is particularly true of the so-called bell 
and spigot pipe which is so commonly used for large water mains. 
At these high resistance joints the current or a portion thereof 
passes in a shunt path through the earth around the joint. This 
causes an eating away of the iron on one side of the joint only, 
if the current flow is always in one direction. 

There are four general schemes now in use for the mitigation 
of electrolytic effects in metal pipes, cable sheaths and under- 
ground structures. 

The first of these schemes provides for an insulated return 
conductor. This is the most reliable method because it elimi- 
nates any leakage of current from street car circuit to ground. 



ELECTROLYSIS 201 

However, there are objections to this scheme including high first 
cost', high maintenance cost, difficulties in insulation, and 
complication at crossings and in car equipment. Under this 
classification of insulated return conductor systems are the double 
trolley system found at present in Cincinnati, Ohio, Key West, 
Florida, and Havana, Cuba, and the underground conduit system 
as used in Washington, D. C, and New York City. In this con- 
nection it might be mentioned that tests made on long lines of 
well-bonded tracks having no intersections to cause complica- 
tions and having the roadbed well drained, show that the leakage 
from the rails to earth is almost entirely eliminated because of the 
high resistance of the leakage path. 

Another of the schemes for reducing electrolysis has for its 
basic principle the reducing of current flow in pipes by surface 
insulation of the pipes or by means of insulating or resistance 
joints. Surface insulation of pipes is not very common at 
present. It is open to the objection that, in a positive area, any 
shght failure in the insulation leads to excessive, electrolysis 
at one point and consequent pitting of the pipe. No paint, 
treated textile, or tarred paper is absolutely impervious to mois- 
ture. Once moisture has penetrated to the pipe, electrolysis is 
set up and a failure in the insulating covering results, due to 
the pressure of the gas formed by electrolysis. However, the use 
of such insulating coverings in negative areas is of decided value. 

The use of insulating joints at frequent intervals in a pipe line 
is to be considered as very good practice for reducing current 
therein. On the other hand, from an economic standpoint, on 
account of the high first cost of such joints, especially in old pipe 
lines, it may not be deemed advisable to depend entirely on this 
scheme for protection. However, as an auxiliary protection 
insulating joints judiciously used are very valuable. 

In mitigating electrolysis by '^pipe drainage" no attempt is 
made to reduce the current in the pipes, but rather to provide a 
metallic path for the current passing out of the pipes. The metal- 
lic path being of lower resistance than the ground path from the 
pipe, little electrolysis will result where such bonding is installed. 
The ordinary method of "pipe drainage" consists of electrically 
connecting the pipes and tracks together by metallic bonds at 
places where the pipes are positive to the rails. Another form 
of "pipe drainage" consists of negative feeders running direct 
from the bus bars to different points of the pipe system. 



202 



ELECTRIC RAILWAY ENGINEERING 



The chief objections to ''pipe drainage" are, first, that the 
system is wrong in that its use involves an increase in the current 
in the pipes and a corresponding increase in electrolysis at high 
resistance joints in obscure and unlocked for places; second, that 
unconnected pipes will be at a higher potential than the bonded 
pipes, thus causing leakage of current between them as indicated 
in Fig. 79; third, that the appHcation of this scheme requires 
that the pipes be electrically continuous for the entire length 
through which current flows; fourth, and lastly, that the remedy 
when applied is not permanent and requires continual attention, 
as the street railway load may change materially or the pipe 
system may undergo changes which will markedly affect the 
current flow in the pipes. 




Water Pipe 
Fig, 79. — Current with portion of pipe system bonded to rail. 

" Track drainage " possesses an advantage over ''pipe drainage " 
in that it seeks to remove the cause of the trouble, i.e., it elimi- 
nates stray currents in place of directing the existing stray currents 
in such paths that they may do no harm. The use of unin- 
sulated negative feeders for track drainage has found wide applica- 
tion in this country. This scheme amounts to reducing the resis- 
tance of the return circuit. The advantages resulting from this 
scheme are: first, the reduction in potential drop in the rails, and 
a corresponding reduction in electrolysis troubles; second, the 
saving in power; and third, the maintenance of a more uniform 
voltage on cars. 

In the insulated negative feeder system, instead of connecting 
the track rails directly to the negative bus bars and thus depend- 



ELECTROLYSIS 203 

ing on the conductance of the rails and whatever copper may be 
in parallel for conducting the current back to the power station, 
this connection at the power station is either eliminated or made 
through a suitable resistance. Insulated return conductors are 
installed at various points on the track system from the negative 
bus bar or from a negative booster, the other terminal of which is 
connected to the negative bus. Two important results are 
attained by this scheme. First, the current being drawn from the 
rail at various points, high current densities in the rails are avoided. 
Consequently, the potential gradient in the rail is much reduced. 
Secondly, by properly designing the negative feeders the potential 
drop in each of the feeders can be made nearly the same, or by 
placing negative boosters in each group of feeders the potentials 
of the rails at the points where the feeders are tied may be made 
nearly the same. In either case the flow of current in the track 
can be subdivided so that the direction of flow will be frequently 
reversed, thus eliminating the possibility of an accumulation of 
large potential differences between widely separated points on 
the track. 

The need of regulation of this phase of electric railway opera- 
tion is receiving increasing attention from the legislative bodies 
of the various municipalities. Chicago has had an electrolysis 
ordinance for a number of years. Recently the ordinance was 
revised. Originally it specified a maximum possible rail drop 
of 25 volts in the city. It now provides for the division of the 
city into three zones. AU uninsulated electric return circuits are 
to be so arranged that between any two points on any uninsulated 
portion of the circuit the sustained maximum difference of poten- 
tial shall not exceed 10 volts in the inner zone, 15 volts in the 
middle zone and 20 volts in the outer zone. 

Two tests are employed in locating electrolysis trouble, the 
current survey and the potential survey. The current survey 
involves the measuring with a milli-voltmeter of the potential 
drop in definite lengths of the pipe under test, and from this data, 
pipe data, and an application of Ohm's law determining the current 
flowing in the conductor. The potential survey consists of 
flnding the difference of potential existing between the metalHc 
grounded conductor under test and adjacent rail or other grounded 
metallic conductors. The purpose of this survey is to show 
where, along the line, it is possible for current to flow from one 
conductor to another. 



204 



ELECTRIC RAILWAY ENGINEERING 



As a result of tests made by representatives of the National 
Bureau of Standards it was found that the average potential 




Fig. 80. 



gradient expressed in volts per 1000 ft. was 0.47 for the insulated 
feeder system and 0.91 for the uninsulated system. The follow- 
ing tests indicate very closely the advantages of the insulated 



ELECTROLYSIS 205 

system and the reduction in current in pipe lines which may be 
secured by its use. 

Total current re- 
turned by pipe lines 
in amperes 

Uninsulated feeders, pipes drained 847 . 4 

Uninsulated feeders, pipes undrained 275 . 7 

Insulated feeders, pipes drained 86 . 1 

Insulated feeders, pipes undrained 48 . 4 

In some cases, question has arisen whether all the current flow 
in pipes and cables and the damage resulting therefrom could 
be attributed to leakage from a railway system. Graphs of tests 
taken simultaneously with station load curves, similar to those 
of Fig. 80, show conclusively by coincidence of peaks whether 
or not the cause may be charged to any particular system or 
station. 

That the problem of electrolysis and its remedy is no small 
engineering task has been proved by the fact that no complete 
relief has been found after many years of study, although very 
recently much has been done to mitigate this evil. That the 
economic problem involved, especially in the large cities, is one 
of great moment is indicated by the fact that estimates of cost 
of meeting the new municipal ordinance in Chicago range from 
$3,000,000 to $4,000,000. 



PART III 

EQUIPMENT 



CHAPTER XIX 
SIGNAL AND DISPATCHING SYSTEMS 

The problem of dispatching cars and of protecting one car 
from another on the same section of track is largely confined to 
interm'ban systems, for in the case of city railways, speeds are 
low, the headwaj^ is small, and double tracks are commonly in 
use. Cars are therefore usually operated as closely as possible 
on a predetermined schedule by the car crews and considerable 
responsibilit}^ is placed upon them for the regaining of schedule 
time in case of delay. In many cities branch line dispatching is 
done b}'' a starter stationed in the city square or at the junction 
point of branch line and the main tracks. For these reasons, 
therefore, this chapter will be principally devoted to interurban 
sj^stems, although the possible application of a number of signal 
systems to urban car operation will be obvious. 

A complete system of train dispatching by a single dispatcher 
for the entire road does away to a large extent with the necessity 
of signals other than those under the control of the dispatcher in- 
stalled for the purpose of attracting the attention of a train crew 
for special orders while enroute, or to stop a car in case of an error 
in orders discovered after the last communication with the crew. 
Most of the signal systems are therefore operated in conjunction 
with a dispatching system and act as a check thereupon. Some 
of the more complete systems, however, are operated with little 
attention from the dispatcher and the complete automatic block 
signal system may be practically independent of dispatcher's 
orders. 

Where a dispatching system is adopted, those signals commonly 
used in steam railroad practice are occasionally found on electric 
lines, involving the manually operated signals and telegraphic 
train orders to way-station agents. Even the ''staff" system 
which is used extensively in England may occasionally be found. 
This is really a combined signal and dispatching system consist- 
ing of two electrically interconnected mechanisms, one at either 
end of a block, which permit a staff to be removed therefrom if 
14 209 



210 ELECTRIC RAILWAY ENGINEERING 

there be no train in the block ahead. A second staff cannot be 
removed from either of the terminal stations until the missing 
staff has been replaced at the farther end of the line. This sys- 
tem not only protects the block but also gives the train crew 
tangible evidence that they have the right-of-way in the block. 

The dispatching system most common to electric railways is 
that using the telephone for communication between dispatcher 
and train crew. Either telephone booths are provided at sidings 
or a portable telephone is carried on each car which may be 
readily connected with the telephone circuit paralleling the 
track by means of a flexible cable and two-pole plug switch. 
It is customary to require the motorman to receive the orders 
and write same on an order blank which furnishes a carbon 
copy for the conductor. The order is checked by the conductor 
reading from the carbon copy to the dispatcher over the tele- 
phone. This check message is either O.K'n or corrected by the 
dispatcher. Whereas there are many modifications of this 
method in use, the telephone is very generally adopted and has 
proved very satisfactory. In fact a large number of the steam 
railroad trunk lines have adopted the telephone in place of the 
telegraph for train dispatching. 

Such telephone lines should be constructed for dispatching only, 
the business to be transacted between other officials or depart- 
ments of the road being provided for by another line. This 
duplicate line is fully warranted in the interests of safety and the 
avoidance of train delays. Care should be taken also to insist 
upon the repetition of orders, for serious wrecks have occurred due 
to the train crew receiving but a portion of the order or mistaking 
an order given to a crew at the dispatcher's office with the receiver 
off the hook for an order intended for them. The repetition of 
an order will correct these errors. 

Signal Systems. — Returning to the signal systems which usually 
augment but may replace the dispatching system, it may be said 
that the present systems have been a gradual growth from the 
single incandescent five lamp series circuit between trolley and 
ground to the more elaborate automatic block signals similar to 
those used on steam roads which are now being rapidly adopted 
by the large interurban railroads. 

For protection against accidents and in order that the schedule 
may be maintained, it is desirable that the train crew should 
know upon .entering a block or certain section of the road : 



SIGNAL AND DISPATCHING SYSTEMS 211 

1. Whether there is another car in the block. 

2. How many cars there are in the block. 

3. What direction the cars are going. 

The last requirement is, of course, applicable to single-track 
roads only. As a matter of fact, nearly all signals are confined to 
the first class only or the first and third classes, but very few in 
general use answer the second question. In order to do this 
automatically, complex circuits, which involve difficulties and 
excessive expense in their maintenance are required. Signals 
displayed on the cars are often used to signify that another car 
is in the same block. 

As to the method of signal control, commercial signaling 
systems may be divided into four classes: namely, manual, 
dispatcher's, intermittent, and continuous track circuit. The 
distinctive features and applications of these systems will now 
be discussed. 

Block Signals. — A "block" as defined by the American Rail- 
way Association is ''a length of track of defined limits the use of 
which by trains is controlled by block signals." If but one train 
is permitted in a block at a time, the system is known as an '' ab- 
solute" block system. Where two or more trains, going in the 
same direction, are permitted in a block at the same time, the 
system is called a ''permissive following" block system and it 
must be so arranged that the ''following" trains will receive a 
*' caution" signal at the block entrance. Permissive systems are 
often used where the traffic is fairly dense and trains operate at 
low or medium speeds. In order to insure safety, the absolute 
system should be used where the trains are operated at high 
speeds. 

The length of block used varies greatly and depends on local 
and traffic conditions. For heavy, high speed service, blocks 
vary in length from 2,000 ft. to 2 miles. For interurban service 
they may extend from siding to siding. In general they must be 
sufficiently long to enable a heavy, high speed train to stop within 
their limits and yet short enough to permit the smallest safe head- 
way between trains to be used. 

At the entrance to each block a signal must indicate, both by 
day and night, whether or not there is a train in the block. Such 
a signal is termed the "home" signal. In addition it has been 
found advisable, if high speed trains are to operate smoothly 
without frequent periods of slow-down, to install an additional 



212 ELECTRIC RAILWAY ENGINEERING 

signal, usually upon the same standard as the home signal, to 
indicate the condition of the next block ahead. This signal is 
termed the ''distant" signal. 

These indications are often given in daylight by means of a 
semaphore and at night with colored lights, although many 
of the signal systems recently developed for use on electric roads 
use light indications for both day and night. In order to make 
the lamps visible in daytime the lamp cases are deeply hooded. 
The use of lights lowers the first cost and maintenance expense 
of a signal system and has been a great factor in the development 
of automatic block systems for electric railways. The lamps may 
be lighted from the signal power circuits and where the con- 
tinuous track circuit system of control is used, if desired the 
connections can be so arranged that the lamps are lighted only 
when the signal is being approached by a train, thus cutting 
down the expense for power and lamp deterioration. As con- 
siderable trouble has been experienced from the use of colored 
*'bulls-eyes" or signal ''roundels" at night upon roads using 
the very powerful headlights owing to reflections from un- 
lighted roundels appearing as signals, it is believed that if the 
more powerful headlight is adopted the semaphore or ''position" 
signal will be ultimately very generally used as a night signal as 
well in the more expensive types of signal systems, being suf- 
ficiently well illuminated by means of the headlight to permit 
the accurate reading of signal aspects. ^ 

In some types of semaphore signals three angular positions are 
used, a 45 deg. position indicating "caution" and a vertical posi- 
tion "proceed" or "clear" aside from the horizontal or "danger" 
indication. The corresponding signals at night are usually red for 
"danger," green for "clear" and yellow for "caution," although 
the latter two colors vary somewhat for the different roads. 
While in steam road signaling one of the right-hand quadrants 
is usually used, the overhead distribution system of the electric 
railway practically compels the use of one of the left-hand 
quadrants where semaphore signals are used. The American 
Electric Railway Association^ has adopted as standard, a three- 
position signal operating in the upper left-hand quadrant with 
signal aspects as shown in Fig. 81. 

1 "Headlight Tests" by C. F. Harding and A. N. Topping, A. 1. E. K, 
Vol. XXIX. 

2 Proceedings A. E. R. A., 1912. 



SIGNAL AND DISPATCHING SYSTEMS 



213 



Fig. 82 illustrates a semaphore signal manufactured by the 
General Railway Signal Company. In two-position signaling, 
the semaphore when in a horizonal position indicates ''danger," 
while the ''proceed" or "clear" signal is usually indicated by 
a 60 deg. angle from the horizontal. 

As the train arrives at the entrance of a block the home signal 
denotes the condition of the first block and the distant signal 
that of the second block ahead. With both at "danger" the 



Stop 



Proceed 

with < 

Caution 



Stop and Stay 



Stop and Proceed 



Proceed, next 
Signal at Stop 



T ^ 



<^ 



Proceed under 
ControKPrepared 
to Stop Short of any 
Obstructions) 



a 



^ Green ^ Green 
O O 



Fig. 81. — Standard three-position signal aspects. 



two blocks ahead are occupied and the train stops. With the 
home signal at "clear" and the distant signal at "danger," the 
first block is clear and the second occupied. The train may 
enter the block under control. With both signals at "clear" 
the engineer knows that two blocks ahead at least are clear and he 
may enter the block at full speed. The distant signal at the 
first block and the home signal of the second block are so inter- 
locked that the former cannot move to "clear" until the latter 



214 



ELECTRIC RAILWAY ENGINEERING 



has attained a similar position. Upon entering the first block 
under control with the distant signal at ''danger" it is expected 
that the next home signal will be at ''danger." Since, however, 
the signal may have changed before the train reaches the second 
block, it is often advisable to install a second distant signal 
within safe stopping distance of the second block. This is 
especially true if the second block signal is not readily seen 




Fig. 82. — Three-position semaphore signal. 



at some distance, since it avoids slowing down if the second block 
has been cleared in the meantime. 

While it is unnecessary to describe in detail the operation of 
the semaphores and colored roundels in their various forms, 
it may be said that their movement is accomplished by means 
of mechanical levers and bell cranks. These levers are operated, 
either electrically by means of solenoids or series motors, or 
through the agency of gas or air pressure in the base of the 



SIGNAL AND DISPATCHING SYSTEMS 



215 



signal. The control of the local apparatus at the signal by- 
means of electric relay circuits is, however, of greatest im- 
portance and will be explained in detail later. 

Manual Control Block System. — Probably the most simple 
arrangement used as a signal, and one to which several roads 
have returned after trying out the more nearly automatic types, 
is that shown in Fig. 83. This consists of a series of five in- 
candescent lamps connected as shown by means of a double- 
throw switch between trolley and ground, two of each group 
being located at one end of the block and three at the other. 
The group of three lamps is placed behind a white or green 
lens and the two lamp group provided with a red lens. Upon 
entering the block the circuit is closed by means of the switch 
which lights a red light at the opposite end and a white or green 

Trolley 



R 

-0-0-| 



r^ 



a 6"n c \d 



a' r 



c' \d 



G-=- 



Fig. 83. — Simple lamp signal. 



light at the entering end. Upon arrival at the other end of the 
block the lights may be switched out and the circuits are such that 
the lights may then be lighted from either end. An extra circuit 
duplicating that of Fig. 83 should be provided, however, for 
operation in both directions. The advantages of this signal 
are its simpHcity and the necessity of one of the crew leaving 
the car, w^hen stopped, to operate the signal switch. Its dis- 
advantages are that the signal light may be extinguished and 
the signal reversed from either end with a car still in the block, 
and if the switch be accidentally left in the off position the signal 
cannot be operated from the other end. This system is, of 
course, suitable for use only on roads on which the cars are 
operated at low speeds and where the traffic is relatively light. 
Another type which has been used in the past to a considerable 



216 ELECTRIC RAILWAY ENGINEERING 

extent on steam roads and which has been installed on a few 
electric roads, makes use of block sections, at the ends of which 
are located block control stations or '^ cabins.'^ An operator 
stationed in one of the cabins receives information concerning 
the condition of a given block by means of the telephone or 
telegraph from the operator at the other end of the block and 
sets the signals accordingly. As the safety of operation depends 
on the accuracy of the human element in the system, it is being 
rapidly displaced by other systems. Also, it is very costly to 
operate. When the operators receive instructions direct from 
the train dispatcher, this system becomes a type of dispatcher's 
control system. 

Controlled Manual Block. — This is in general similar to the 
manual system just described except that the signals are elec- 
trically interlocked so that if the signal at one end of the block 
indicates danger, the signal at the other end cannot be made 
to indicate ''clear." The ''staff" system described on page 209 
is another form of controlled manual block. 

Dispatcher's Control Systems. — A common form of this sys- 
tem employs signals located at sidings, stations, and other points 
along the line at which the dispatcher may wish to communicate 
with a train crew. These signals are selectively operated by 
synchronous impulses sent over lines connecting the signals with 
the dispatcher's office. The dispatcher can stop a train at a de- 
sired point by operating the signal located at that particular 
point. Communication between the train crew and dispatcher's 
office is obtained by means of a telephone system as described 
on page 210. 

A type of dispatcher's control signal recently developed has 
many unique and valuable features. This type is known as the 
Simmen signal, and has been installed on several roads within the 
last 3 years. In this system three sections of insulated third 
rail, each about 75 ft. in length, are spaced about 2000 ft. apart 
at each siding. Each group of three sections is connected by 
means of a line wire, through a control switch mounted on the 
dispatcher's desk, to a storage battery, one side of which is 
grounded. These switches have three positions, right, left, and 
vertical. In the vertical position, the contacts are open and the 
third rail sections to which that particular switch belongs are not 
energized. The dispatcher sits with his back to the track and 
when he wishes to signal a train moving toward his left, he throws 



SIGNAL AND DISPATCHING SYSTEMS 



217 



the switch which is connected to the next siding ahead of the 
train to his left. Adjacent switches are mechanically inter- 
locked, so it is impossible to throw one of them to the right and 
the other to the left and thus allow two opposing trains to come 
together in a block. Fig. 84 is an illustration of the dispatcher's 
desk. 

Each car is equipped with an insulated third rail shoe and when- 
ever the shoe is resting on an energized third rail, a grounded 




Fig. 84. — Dispatcher's desk. Simmen signal system. 



circuit through a relay mounted on the car is completed and a 
green lamp located in the motorman's cab is lighted. The lamp 
is on a local circuit fed from a storage battery which is carried on 
the car. The relay also has its winding connected in a second 
local circuit through a front contact on the relay, and a switch 
mounted in the third rail shoe which is so constructed as to be 
closed when the shoe is not resting on a third rail. Thus the 
local circuit which contains the green lamp remains closed after 
the car has passed an energized third rail section giving the 



218 ELECTRIC RAILWAY ENGINEERING 

motorman a continuous clear signal in the cab. If for any reason, 
due either to the failure of the signal system or to the fact that the 
dispatcher has placed the control switch in the vertical position, 
a third rail section is de-energized, the relay of a car passing over 
that section will also be de-energized and the relay armature 
through a back contact will close a third local circuit containing 
a red lamp, thus extinguishing the clear signal and giving a 
danger signal. This danger signal will be displayed until the 
car again passes over an energized third rail. A car receiving a 
stop signal at the first of the three third rail sections can, if no 
opposing car is in sight, proceed slowly to the middle section. 
If it receives a clear signal at this section it can proceed; if the 
signal still indicates danger the car is required to stop. By 
stopping immediately over the third rail section the crew may 
communicate with the dispatcher, using the control circuit as a 
telephone circuit. The red lamp circuit may also be used to 
operate a relay which will open the power circuit of the car and 
set the air brakes. 

A device, see Fig. 84, in the dispatcher's office provides an 
automatically printed record which shows the positions and 
movements of all trains along the line. 

While this system is more costly than the simpler forms of dis- 
patcher's systems, it is not as costly as the various forms of track 
circuit systems and it reduces dispatching errors to a minimum. 
The use of the cab signal obviously has many advantages over 
other types. 

Interriiittent Control Signals. — Elaborating upon the principle 
of the simple lamp signal. Fig. 83, and adding various automatic 
features, several companies have developed signal systems for 
both single- and double-track roads which have been widely 
adopted. A representative type built by the United States 
Signal Company will be described. It operates from the trolley 
circuit and consists of one signal box and trolley switch at either 
end of the block connected as in Fig. 85 and requiring two wires 
throughout the length of the block. A car entering the block 
at A makes a momentary connection between the trolley wire and 
wire No. 4, as the trolley wheel operates the iron tongue switch 
mounted on the trolley wire. This momentary connection, closing 
a circuit to ground through a relay and a suitable resistance, 
completes the permanent circuit connecting the trolley wire 
through No. 1, the green lamp at A, the signal fine wire, the red 



SIGNAL AND DISPATCHING SYSTEMS 



219 



lamp at B, through resistance in box B to ground. Other cars 
entering at A do not change the signal setting, but a car leaving 
the block at B energizes wire No. 5 through the agency of the 
overhead trolley switch and trips the relay which extinguishes 
the red light. A car entering at B performs the reverse operation, 
lighting the green light at B and the red signal at A. The boxes 
and switches are therefore interchangeable. Red and green 
disks are displayed in some types of this signal for day use, al- 
though the lights are commonly used as day signals as well. 
This type of signal has given a fair degree of satisfaction although 
its maintenance expense is high, especially because of damage by 
lightning. In fact it is very difficult to design a signal operating 
upon a grounded circuit which will not be seriously affected by 




Trolley 




RO 
i^o9 



Fig. 85. — United States signal. 



lightning. The widely varying voltages on the various sections 
of the average interurban line also introduce difficulties in the 
design of signals to be operated from the trolley circuit. It should 
be noted that in this system the motorman is assured that the 
red signal has been displayed at the farther end of the block if 
the green light appears at the entering end. This fact is seldom 
determined by the steam railroad engineer who relies upon the 
automatic block signal to give the danger indication without 
actually observing the signal movement himself. It should also 
be noted that the car controls the signals only as it enters or 
leaves the block and that while within the block it has no con- 
trol over the signals. 

On account of its comparatively low first cost, the intermittent 



220 ELECTRIC RAILWAY ENGINEERING 

control type of signal has been used quite widely in both inter- 
urban and suburban service in the past. Present practice, how- 
ever, seems to tend toward using it in suburban service only. 

Some of the more recent types allow permissive following move- 
ments by adding a device which counts the cars *'in" and ''out" 
of a block and does not permit the signals to return to ''clear" 
until all cars have been counted out. The signal aspects also 
conform to the latest recommendations of the American Electric 
Railway Association, namely:^ 

"Red: Stop, do not operate trolley switch. 

Green: Proceed by trolley switch to operate signal. Proceed if 
green aspect changes to red light over yellow light on passing trolley 
switch. 

Red and Yellow: Block is occupied by a car running in the same 
direction. Proceed by trolley switch and if yellow light changes to the 
opposite side of the red one, proceed under control." 

To give these aspects or indications four lamps are required, 
one green, one red, two yellow. The yellow lamps are arranged 
side by side just below the red one. 

Steam Railroad Practice. — As the track circuit block signal 
systems used with electric roads have been patterned after the 
more simple steam railroad installations a description of the 
latter will aid in understanding the former. The two rails, 
Fig. 86, for a block in length are insulated from one another and 
also from the adjacent rails of neighboring blocks by means of 
insulating rail joints (C). The various rail lengths of a single 
block are bonded together in a manner similar to that described 
in Chap. XVII, but with much smaller wire bonds. A gravity or 
storage battery Z) of 1 or 2 volts e.m.f., located in a manhole below 
the frost line, is connected between the rails at one end of the 
block. At the other end of the block a sensitive relay R is con- 
nected across the two rails. This relay is usually mounted in 
the base of the signal tower and thereby protected from the 
weather. Where there is no train in the block the battery sup- 
plies current to the relay by way of the two rails and the signal 
is held in the ^' clear" position. As the first trucks W of a train 
enter the block, however, the wheels and axles short circuit 
the relay and it opens, closing the local circuit which throws 
the semaphore and colored roundels into the "danger" aspect. 

1 Proceedings A. E. R. A., 1913. 



SIGNAL AND DISPATCHING SYSTEMS 



221 



The signal is locked in this position until the movement of the 
last truck of the departing train from the block removes the 
short circuit, closes the relay and clears the signal. 

Such is the very simple circuit and mechanism of the automatic 
block signal for steam railroads, and although its first cost has 
been sufficiently high to render its adoption rather slow, its 
maintenance is not excessive and its positive operation is to 
be depended upon. In fact, in one instance but one failure to 



Signal Motor 

Mechanism 

(M) 




Fig. 86. — Perspective of track circuit.^ 

operate in 250,000 was the record of operation on a large signal 
system during the period of 1 year. 

Track Circuit Block Signals. — With the electric railroad, which 
makes use of the track rails for the return of heavy currents to 
the substation or power house, the problem becomes a more 
difficult one, as the rails are no longer free for sectional insula- 
tion as in the case of steam roads. One method of overcoming 
this difficulty which would naturally suggest itself is to use one 
rail for signal purposes and the second rail for the return of power 
1 Reproduced from General Railway Signal Co. publication. 



222 



ELECTRIC RAILWAY ENGINEERING 



current. The further use of alternating current for the signal 
relay would permit selective operation of the latter without inter- 
ference from the power current. Such a system is successfully 
used in the New York subway, its principle of operation being 
illustrated by Fig. 87. 

By referring to this figure it will be seen that one rail, termed 
the ''block rail," is insulated in sections one block in length, 
constituting a circuit for signal current only. The other rail 
carries the current from the trains and also acts as a common 
return circuit for the signal system. Alternating current for 
the signal circuit and also for the signal lamps is supplied through 
transformers from single-phase alternating current mains 
paralleling the track. If the power current is flowing in the 

Trolley or Third Rail 




i^m 






D.C. Railwaj^y< 
Generator-^'^^ 
Return Rail 4, — ^ \ — 



Signal 
Signal Light- 



n 



Block Rail 



&5 



vvwJ 

N'WAA/I 



Fuse -> 
Non .inductive 
Resistance 
Reactance Coil 

Track _^ 
Transformer 

-^A.C. Track 
—J Relay. 



r 



i^ 



Rail Insulation 



'\ ^' I Signal A.C. 
^ ^ ^U Generator 



A.C. Signal Mains 



Fig. 87. — Single rail alternating current block signal. 



return rail from left to right, the voltage between rails at B will 
be slightly less than at A due to the fall of potential in the rail. 
This will cause some of the direct current to pass through the 
relay connected between the rails at A, thence through the 
block rail and the transformer secondary to the return rail 
at B, the latter forming a high resistance shunt path to the 
length of return rail AB. In order to limit the amount of this 
current which would otherwise produce a uni-directional mag- 
netic field in the relay and transformer, high non-inductive re- 
sistances are inserted in series with the relay and transformer 
secondary and a reactance coil shunted across the relay. While 
the direct power current following the block rail will pass freely 
through this reactance, the signal alternating current will be 



SIGNAL AND DISPATCHING SYSTEMS 



223 



prevented by the impedance of the reactance coil from taking 
that path and will therefore pass through the relay. As an 
additional precaution in the case of the transformer an air gap 
is introduced into the magnetic circuit to reduce to a minimum 
any magnetic flux which might be produced by the relatively 
small leakage direct cm-rent. 

With these added precautions the relay system operates 
exactty as in the case of steam railroad equipments with the 
exception that the relay must be of the alternating current 
type. A relay depending upon the torque produced by eddy 




Fig. 88. — A New York Subway signal installation. 



currents induced in an aluminum disc being acted upon by the 
magnetic field set up by the current in the relay has been adopted 
for this purpose. 

In the case of the particular installation of this system in the 
New York subway, the alternating current distribution is at 500 
volts and 60 cycles, the track transformers stepping the potential 
down to 10 volts, while the signal lamps are operated at 55 volts. 
The resistance of the track and signal circuit is such as to im- 
press approximately 5 volts upon the relay. The power factor 
of the circuit is in the neighborhood of 80 per cent, and the 
power taken by an average block but 80 watts. A typical 
installation is represented in Fig. 88. 



224 



ELECTRIC RAILWAY ENGINEERING 



Block Signals for Alternating Current Roads. — When the 
problem arose to equip electric roads operating with alternating 
current in the track rails, it may be readily seen that still further 
difficulties were encountered. The problem was fairly well 
solved, however, by the development of the two rail signal 
system making use of inductive bonds, Fig. 89, and this solu- 
tion marked the beginning of a new era in the development of 
railway signal systems. Practically all of the automatic block 
signals which are being installed on both alternating and direct 
current electric railways at present are of this general type. 
They are also being installed on a number of steam roads, the 
high battery maintenance expense of the older types of steam 



#l2s3??2ts;:. 




Fig. 89. — Inductive bond. General Railway Signal Co. 



road signals more than offsetting any disadvantages possessed 
by modern alternating current signals. The fact that state 
laws in some states require the installation of automatic block 
signals of a type satisfactory to their railroad commissions on 
all railroads operating within their limits has done much to 
hasten the development of a cheap and reliable automatic block 
signal operated with track circuit control. 

The principle of this type of signal system, similar to that 
operating on the single-phase terminal electrification of the 
New York, New Haven & Hartford Railroad in New York, is 
illustrated in Fig. 90. It will be seen that each rail is insulated 
at the ends of the block as in the case of steam railroad practice, 



SIGNAL AND DISPATCHING SYSTEMS 



225 



but inductive bonds are installed between the rails Sit AB and 
EF of sufficient current carrying capacity to carry the train 
current. The middle points of adjacent bonds are connected 
together so that there is a complete electrical circuit from train 
to power house by way of each rail, this circuit involving one- 
half of each bond at every block. This connection tends to 
neutralize the e.m.f.'s, due to the power current, w^hich are set 
up in the inductive parts of each bond. These bonds are care- 
fully designed so that their counter e.m.f., due to any unbal- 
ancing of the power current in the rails, will not be great at the 
frequency of 25 cj^cles or below, at which the train motors operate, 
but will be sufficienth' great to produce a useful difference of 
potential between the rails in the signal circuit which is operated 



Trolley 



RaiV Insulation 




D.C. Rail-way,^, Q , 
Generator ^ 



^cj>^\ 



■Ipiductive Track ty ^ i^ducti%^e 



Relaj^ 



A.C. Signal Mains^ 



,^vv\\ Bonds 
Track 
Transformer 



^ 



A.C. Signal 
Generator 



Fig. 90. — Double rail alternating current block signal using inductive bonds. 



at 60 cycles. In other words, a very interesting appUcation is 
made of the theory that the reactance of a coil is proportional 
to the frequency and the bonds are therefore designed to operate 
upon one frequency only. 

The immediate source of power is the transformer as in the 
single rail system, but in this case the power current is sufficiently 
well balanced in the two rails to prevent unbalanced currents 
flowing in the transformer and the au' gap in the magnetic 
circuit is therefore omitted. The transformer is designed with 
a relatively high leakage factor, however, in order that the current 
may not be excessive when the secondary of the transformer is 
short circuited by the train in the block. It w411 be noted further 
that for the above reasons the auxiliary resistances and react- 
ance shunt across the relay may be omitted. 

15 



226 ELECTRIC RAILWAY ENGINEERING 

With these- changes and a slight change in the design of the 
relay, the system operates as in a single rail design. The direc- 
tion of the power current is shown by full lines and that of the 
signal current by dotted lines in Fig. 90. 

In all of the foregoing automatic block systems it should be 
noted that if the track relay circuit be opened the action is the 
same as though the relay were short circuited by a train in the 
block, i.e., the signal is thrown to ^Manger.'' This action has 
proved of great value in detecting broken rails and has probably 
prevented a number of wrecks thereby. 

Single-track Signaling. — The continuous track circuit signals 
just described were developed for use on double-track roads. 
Suitable signals of this type for use on single-track roads are a 
very recent development. On a single-track road the block 
signal must guard against both following and opposing move- 
ments. The system must be an ^'absolute*' block for opposing 



G R Y Y R G ^-^ G R Y Y R G ^\ G R Y Y R G 

@2)-®— |-®-<S^ -(oESH3>-|-@-@S) ^(Sr^Mo)— I— (SHonS) 

West \ ^v ' ' East 

A B^ C D,^ E F 

Fig. 91. — Single-track signals with preliminary track circuits. 

movements and may be either "absolute" or "permissive" for 
following movements. 

The signals on a single-track road are controlled by relays 
similar in design to those used in double-track systems, being 
more a difference in arrangement of apparatus and connections 
than a difference in the fundamental apparatus. 

Fig. 91 shows the arrangement of the signals in a single-track 
block system, manufactured by the General Railway Signal Com- 
pany, which is being used on a number of interurban roads at 
present and illustrates a method of diagramming signals which is 
commonly used by signal engineers. 

A typical installation of this type of signal is shown in Fig. 92. 

The line WE represents the track. Three sidings with centers 
at A, C and E are shown. The block length is AC (or CE). 
The dashed lines parallel with the track indicate the controlling 
limits of the various signals, i.e., a car on the track under a dashed 
line causes the signal to which the dashed line is connected to 
operate. Ends of track circuits are indicated by a short line 
drawn at right angles across the track. The track between the 



SIGNAL AND DISPATCHING SYSTEMS 



227 



right angle marks on the sidings is not connected to the signal 
system. The various signals are 1, 2, 3, etc. Pairs of signals 
such as 1 and 2 are of course mounted in a single lamp housing 
located either on a line pole or special signal mast; the signals, 
however, are shown as pointing in the direction of the traffic 
which they control. Since this system permits following move- 
ments, three lamps are required. The sections AB, CD, etc., are 
known as ''preliminaries." Their function in this particular 
system is to guard against the possibility of two opposing trains 
entering a block at the same instant and thus neither one getting 




Fig. 92. — Typical installation, single-track signal. General Railway 

Signal Co. 



a stop indication. The length of these preliminary sections 
depends on the distance covered by a train in making a service 
stop and varies from 1000 ft. to 3000 ft. 

The operation of the system is briefly as follows: 
Assume an eastbound train approaching A. If the block AC 
is empty, signal (2) will indicate clear or the green lamp will be 
lighted. As the train passes A the green lamp will be extin- 
guished and the yellow lamp will be lighted giving a permissive 
signal to a following train. At the same time signal (3) indicates 
red, thus blocking all opposing movements at C. The block 
indicator h, which is a sort of distant signal placed at the begin- 



228 ELECTRIC RAILWAY ENGINEERING 

ning of the preliminary section, is lighted whenever the block AC 
is occupied. A westbound train entering the prehminary CD 
causes signal (2) to indicate red but does not affect (3) until it 
reaches C. Thus, if a westbound train passes D at the same 
instant an eastbound train passes A , the eastbound train will not 
receive a danger indication but the westbound train will be 
stopped at C. In order to facilitate switching operations a 
special device controlled by the track circuits and known as a 
switch indicator is used. This indicator is placed at each 
switch and shows whether or not the block is clear. If desired, 
three-position semaphore signals may be used in place of the 
lights. 

Another type of signal. Fig. 93, manufactured by the Union 
Switch & Signal Company, which is being installed on a large 
number of electric railways, makes use of ''intermediate signals" 
instead of preliminary track sections to guard against opposing 

•^V '"^N ^ 

\ \ 3^ 

Fig. 93. — Single-track signals with intermediate signals. 

trains entering a block at the same instant. It also permits 
following movements. 

This system is indicated as using semaphore signals, although 
light signals may be used if desired. Only one track circuit per 
block is used and it is fed from the center. Two track relays, one 
at each end of the block, are used. A car entering at A causes 
danger indications to be shown at signals (2), (3), and (5). If 
both cars entered the block at the same instant they would not 
get danger indications at the home signals (2) and (5), but would 
be blocked at (3) and (4) which are staggered enough to permit 
both trains to come to a stop without colliding with each other. 

The permissive following indications are secured in the 
following manner: A car entering the block at A does not cause 
signal (4) to indicate until it is near the center of the block. The 
electrical connections are such that after signal (4) has operated 
by an eastbound train signal (2) will change from the danger to 
the permissive indication, thus allowing a second train to enter 
the block under control. 



SIGNAL AND DISPATCHING SYSTEMS 229 

Cab Signals. — As stationary signals are sometimes obscured 
by smoke, steam, fog or blinding storms, and as train crews are 
not infallible but will sometimes overlook a danger signal even 
when the indication is clearly given, much effort has been ex- 
pended in trying to develop a satisfactory cab signal. One type 
has already been described. A number of other types are being 
tried at present. In general these signals are controlled by track 
circuits similar to those used with stationary signals, use being 
made of a third rail section or other form of contact device to 
communicate the indication to the cab signal. The development 
and installation of a satisfactory type of cab signal will go a great 
way in solving the problem of safe train operation. 

Automatic Train Stops. — Some of the elevated railways have 
used automatic train stops for a number of years. While 
desirable for all classes of service, they are particularly useful 
where trains must be operated at high speeds with short headways. 
One type of automatic stop is shown in Fig. 88. The projecting 
arm outside of the right-hand rail is controlled by the track circuit 
and is raised when the signal indicates danger. This engages a 
rocker arm on the locomotive or first car which operates the air 
brakes if the train moves past the block entrance. Some of the 
roads using automatic stops have found that the installation of 
the stops greatly increased the alertness of the train crew and 
made for better discipline, because the stopping of a train by 
means of the automatic stop is in the nature of a demerit charge 
against the train crew. 

Cost. — According to the Electric Railway Journal^ the costs of 
the various types of automatic signal systems are approximately 
as follows: dispatcher's system (Simmen), $800 per mile; 
intermittent control system, $550 per mile; track circuit control 
system, $1000 to $2600 per mile. 

It may have been inferred from the previous discussion that 
there is a wide variety of signal systems with widely varying 
degrees of protection and corresponding first costs from which 
to choose. The continuous track circuit signals are most re- 
liable in their operation and give the greatest safety of train 
operation, but are the most costly. While a theoretically perfect 
system has not yet been developed, it is safe to say that the more 
elaborate systems have not been cast aside by the interurban 
railroads because of the unsatisfactory design and operating 

^ Electric Railway Journal, Convention Issue, Oct., 1913. 



230 ELECTRIC RAILWAY ENGINEERING 

qualities, but rather because of their high first cost and main- 
tenance charges. As the combined result of some rather serious 
wrecks which have recently taken place on interurban roads, the 
advertising value of a complete automatic block signal system, and 
the increasing pressure which is being brought to bear by state 
railroad commissions throughout the country, it is believed that 
some form of automatic block signal will be pretty generally 
adopted in the near future and the resulting developments in the 
electric signal field correspondingly rapid. 



CHAPTER XX 
TRACK LAYOUT AND CONSTRUCTION 

The electrical engineer of a proposed electric interurban rail- 
way is often called upon to determine the right-of-way and super- 
intend the track survey and construction, although in the large 
city systems or extensive interurban developments a technically 
trained civil engineer is usually given this responsibility. In 
either case the electrical engineer should be famihar with such 
general features of the problem as may be herein outlined. 

Right-of-way. — After several proposed routes have been sug- 
gested for the new railway, possibly with the aid of rough pre- 
liminary surveys for each, and detailed notes taken of the ad- 
vantages and disadvantages of each, involving the topography 
of the country, number of intermediate towns and amount of 
tributary population served, possible schedules, etc., it is neces- 
sary to decide upon one route. This is usually determined by 
the officials of the company in conference with the engineer. 
With this decision in mind the problem of obtaining the right-of- 
way presents itself and it is often policy not to make the above 
decision public until after the greater portion of the right-of-way 
has been secured. In fact it has sometimes been found advisable 
to propose publicly two possible routes and even go to the extent 
of purchasing options on land along each in order that an 
element of competition may enter, preventing land and options 
from assuming exorbitant values along the desired route. 

Great diplomacy must be exercised by the advance real estate 
agent in order to secure the desired route at a reasonable figure 
and without too many concessions, which often complicate the 
schedules and embarrass the company when operation begins. 
It must always be remembered that much of the future traffic will 
come from those with whom these preliminary negotiations are 
made. 

If satisfactory 'locations cannot be secured, either because of 
opposition to the proposed road or too high prices being placed 
upon the land, right of eminent domain may be secured through 

231 



232 ELECTRIC RAILWAY ENGINEERING 

the court and certain sections of the route condemned and thereby 
purchased at a value appraised by the court or a commission 
appointed by the court. As this proceeding makes pubHc the 
proposed route and prejudices some against the company, it 
should be avoided if possible, but if found necessary, it should be 
postponed until the remainder of the lan^ has been secured. 

It will be noted that the above discussion presupposes a private 
right-of-way for the road. Such a route is generally much to be 
preferred except within the limits of intermediate towns, and even 
in the latter case a route but a few blocks from the center of town 
on a back street with little traffic, where speeds may be fairly 
high and frequent curves avoided, should be given serious con- 
sideration. In some instances interurban railroads run for miles 
along country roads, but it is usually done at the expense of low 
schedule speeds and high maintenance charges due to restric- 
tions often imposed by town boards and street commissioners, not 
to mention frequent and serious accidents. A slightly larger first 
cost for a private right-of-way is justified in most cases from the 
standpoints of schedule, safety and independence from ordi- 
nances stipulated by outsiders not only, but from the purely 
financial consideration as well. 

Preliminary surveys will vary from $25 to $30 per mile, while 
location surveys which will furnish all necessary data for the 
closing of the contract will add from $70 to $100 more. An 
average figure of $100 per mile has often been used as an approxi- 
mate estimate of these two surveys combined. The engineering 
cost of roadbed and track may be taken from $1100 to $2000 
per mile, which may represent from 2}^ to 5 per cent, of the total 
cost. These estimates will vary with the difficulties encountered 
and the type and weight of construction adopted. They are 
based upon private interurban right-of-way and will be greatly 
exceeded in city street construction. 

A right-of-way at least 100 ft. in width should be secured to 
allow for possible double track with necessary cuts and embank- 
ments provided with adequate drainage ditches. Such a strip 
of land averages 12 acres to the mile. 

With the route approximately determined and the right-of- 
way secured, a final survey should be made to locate the exact 
line for the track and to determine the profile. With the exact 
profile plotted the grade line may be drawn consisting of an 
average fine through the profile representing a series of grades, 



TRACK LAYOUT AND CONSTRUCTION 233 

with none exceeding 2 per cent, if possible, and with as close a 
balance between ''cuts" and ''fills" as may be secured in order 
that the haul for excavation and embankment may be a mini- 
mum. While grades as high as 7 or 8 per cent, sometimes 
exist on interurban roads, it will often be found that when the 
first cost of the extra heavy car equipment and possibly the 
station equipment necessary to climb these grades together with 
the annual cost of extra power required are balanced against the 
fixed charges on the extra cost of reducing the grade by means 
of a deeper cut or a slight change of route, the latter policy would 
have been the better of the two. 

Before accurate estimates can be made or contracts let for 
preparing the subgrade it will be necessary to learn something 
more of the character of the subsoil. It will be assumed that 
the general nature of the country and its geological formation 
were carefullj^ noted during the preliminary survey, since the 
decision of the proper route depends largety upon such a study, 
especially when a river is to be paralleled and possibly bridged 
occasionally. It is now necessary, however, to have test borings 
made as deep as the deepest proposed cut at intervals along the 
line sufficiently frequent to obtain a good idea of the type of 
excavation to be expected and the necessity of driving piles or 
installing mattress concrete or timber in case of possible quick 
sand. A contract can usually be placed for such borings with 
their results either represented to scale on a drawing for each 
station or, better, by a glass tube filled to scale with the various 
strata of subsoil found. 

With this information at hand a series of cross sections at right 
angles with the base line at stations 100 or 200 ft. apart, or 
possibly less where the profile is very irregular, may be made and 
the volume of excavation and embankment calculated. A list 
of cut and fill expressed in cubic yards of each type of subsoil 
from solid ledge to soft clay may then be made for each mile of 
road and estimates readily calculated and contracts signed. 
Typical sections of cuts and embankments will be found in Fig. 
94, while estimates of their respective costs in the South will 
be found at the end of the chapter. These latter values vary 
greatly with local conditions and are usually based upon a 
certain maximum length of haul between a cut and the corre- 
sponding fill into which the excavated material may be deposited. 

A certain area of so-called "free haul" is established which may 



234 



ELECTRIC RAILWAY ENGINEERING 



vary somewhat for the various stations along the proposed line. 
This ''free haul," which is a convenient unit upon which to 
figure contract estimates and bids, is based upon the distance 
within which excavation may be balanced against fill, due allow- 
ance being made for shrinkage of the latter. Contracts and 
bids usually name a price per cubic yard for grading within the 
''free haul" area and an additional price per unit for all "over- 
haul." The "overhaul" is determined by subtracting the 
"free haul" from the distance between the centers of gravity 
of the remaining excavation and final embankment. 

Excavation and grading may be undertaken in connection 
with small jobs with the use of hand shovels, wheelbarrows, 
scrapers and wagons. Although the unit cost may be higher 
than for larger contracts, the smaller volume handled may 




\, Ja1\\.\ i/LL J \ aNP^^'~" tJnless otherwise 

r^'T^ H*HT-3H ^^ ordered 



,<^^!^\-^-A 



i^6— I 

Unless otherwise 

ordered 



EXCAVATION 




Unless otherwise 
ordered 



Fig. 94. — Typical interurban roadbed construction. 



warrant the selection of this method. For such work as the 
construction of a new interurban line, however, the use of 
power shovels and industrial narrow gauge railway trains hauled 
by dummy locomotives would usually be warranted. A figure 
presented by the Lake Shore & Michigan Southern R. R., quoted 
by Richey, ^ covering the cost of grading third and fourth track 
for the above road with a haul not exceeding 5 miles, is given 
in the following table. This includes loading, unloading and 
leveling ready to lay ties, and covers both labor and supplies. 
It is, however, exclusive of interest, depreciation, explosives and 
overhead charges. 

^ See Richey's "Electric Railway Handbook." 



TRACK LAYOUT AND CONSTRUCTION 235 

Table XXVI. — Cost of Grading 

Gravel pits with 15 ft. face SO. 11 cu. yd. 

Earth cuts 3 to 10 ft. deep 0. 15 cu. yd. 

Shale cuts, all blasted 0.21 cu. yd. 

Rock cuts, requiring blasting and breaking 

up . 25 cu. yd. 

The labor and supplies in the above table are based on the 
following units: 

Foreman $73 . 00 per month. 

Laborers 0. 15 per hour. 

Steam shovel crew (8 men, 10 hours) 25.00 per day. 

Train service, labor and supplies 28 . 00 per day. 

Trestles. — In localities where low elevations must be spanned 
and especially where the subsoil is of questionable bearing 
capacity the choice between wooden trestles, structural steel 
and masonry is often made with difficulty. The Engineering 
News sets forth the following arguments in favor of wooden 
trestles for preliminary construction at least. These are par- 
ticularly forceful, of course, in sections where timber is cheap. 

"A well-built timber trestle, while it lasts, is a very solid and safe 
structure, and it lasts normally in good condition for from 5 to 10 years 
while much hastily built masonry gives out in 1 or 2 years. 

''There is more time to determine accurately the size of opening 
needed and thus avoid needless washouts; besides, well-built timber 
structures are less likely to wash out suddenly. 

"The time of construction is shortened materially, often an important 
consideration. 

''The masonry, when at last built, is almost certain to be better built 
and of better stone. Haul, then, is of less importance and there will 
be more time to secure good materials. The roads are few on which 
any large proportion of the original masonry is in good condition after 
10 years. This is especially true of the smaller structures, such as 
cattle guards and open culverts, which are often so poor as to shake 
to pieces in a few months. The lesson that the smaller the structure 
the larger and better dressed must be the stones composing it, if it is 
to be durable, is one which engineers are slow to learn. 

"It is easier to introduce long and high fills afterward to be filled by 
train, or replaced by masonry or iron, and thus to secure a better align- 
ment and avoid rock cutting or other objectionable work. 

"A very large part of the total cost of the line in its permanent form 
is postponed for 6 to 8 years past the trying years of early operation, 
thus not only saving the interest on the cost of the permanent work but 



236 ELECTRIC RAILWAY ENGINEERING 

going far to protect the company from the danger of early insolvency, 
which has proved so deadly to many overconfident companies. 

"The only necessary disadvantages are the liability to decay and fire. 
To guard against the former is a mere question of inspection. The 
danger from fire is a real one and every year has its record of accidents 
resulting therefrom, but if the danger is real it is small. There are few 
such accidents and those mostly from gross carelessness. In proportion 
to their number, accidents from iron structures have been vastly more 
numerous and more fatal, and the same is true in substance of small 
masonry structures where the great liability to washouts is a serious 
matter." 

Ballast. — It is safe to say that the experience of interurban 
roads which have been operating for some time demonstrates the 
fact that money expended in first-class subgrade construction and 
rock ballast proves to be the most economical in reducing main- 
tenance charges and providing a smooth riding roadbed which 
does not quickly wear out both itself and the rolling stock. 

The ballast, which is that portion of the roadbed upon which 
the ties are placed, should be sufficiently porous to permit the 
water to run off freely. The best ballast is recognized to be 
crushed rock capable of passing through a 23-^ in. ring. Coarse 
gravel, however, makes a very good substitute and is very often 
used because of its lower cost. Fortunate indeed is the road 
that secures with its right-of-way one or more borrow pits con- 
taining good ballast gravel. This ballast is laid for a depth of 
6 to 18 in. under the ties and should cover the ties to the base 
of the rail. 

Gravel ballast will range from 15 to 40 cts. per yard, while rock 
ballast will vary from maximum values of gravel to 75 or 80 
cts. per yard laid in place ready for ties. 

Ties. — Now that the scarcity of good lumber is beginning to be 
felt, with a corresponding increase in first cost, the selection of 
suitable ties and their treatment to insure long life is becoming 
a serious problem. Pine, cedar, white oak, red oak, fir and chest- 
nut are the woods in most common use. The choice between 
these depends largely upon the variety which is native in the 
locality in which the road is being built. Cedar is probably as 
long lived as any, while the ability of white oak to hold spikes is 
probably greater than any other wood. While this variety of 
tie is generally too expensive to use throughout, it is often speci- 
fied for curves where the strain on spikes is of course greatest. 

Herrick gives in the following table an approximate length of 



TRACK LAYOUT AND CONSTRUCTION 237 

life for the different varieties of ties as determined by Mr. Hough. ^ 

Table XXVll.— Life of Ties 

White oak 7.4 years. 

Red oak , 5.0 years. 

Chestnut 7.1 years. 

Southern pine 6.5 years. 

White pine 6.5 years. 

Red cedar 11.8 years. 

It is generally considered advisable to specify preservative 
treatment for ties in order to increase their life, although it is 
difficult to determine from experience thus far just how much 
the life is extended thereby. Probably a fair average price for 
an untreated tie throughout the country is 70 cts. with a possible 
15 cts. per tie increase for treatment. Ties which have been 
embedded in concrete in city construction have shown par- 
ticularly long life, averaging from 10 to 20 years with many rail 
replacements. The replacement of rails and removal and re- 
placement of spikes during realignment often shorten the life 
of a tie when it has not decayed. Screw spikes have been pro- 
posed to obviate this difficulty, but they are little used at present 
because of their higher first cost and the greater time required for 
installation and removal. 

It has been found recently that screw spikes used with chloride 
of zinc treated ties have very short life due to galvanic action 
between the zinc salts and the steel of the spikes. This, together 
with the difficulty noted below which ties thus treated some- 
times introduce in the operation of signals, have brought about the 
rather general use of hard wood ties without treatment or soft 
wood ties confined to creosote treatment. 

Reinforced concrete and steel ties have been experimented 
with, especially abroad. Whereas concrete and steel substruc- 
tures are replacing ties to a large degree in city streets, the wooden 
tie for interurban or steam railroad use has not been replaced to 
any extent in this country. 

The dimensions of ties for interurban use are similar to those 
for steam roads, averaging 6 in. X 8 in. X 8 ft., although 5 
in. ties may be found occasionally. In third rail construction 
a longer tie is installed every 10 ft. to act as a support for the third 
rail insulator. The spacing of ties will be found to vary from 
15 to 30 in., but an average dimension may be taken as 2 ft. Ties 

i" Practical Electric Railway Handbook," by A. B. Herrick. 



238 



ELECTRIC RAILWAY ENGINEERING 



which he under the rail joints are placed nearer together, but 
their exact spacing is dependent upon whether a suspended or 
supported rail joint is used, as will be described later. 

One consideration in connection with the selection of ties which 
has received very little attention is the effect of preservative 
treatment upon their resistance. This is of particular value 
only where the automatic block signals are installed. From the 
discussion of the previous chapter it will be seen that if the resist- 
ance of the ties be greatly reduced they will act as a shunt to the 
relay and possibly interfere with its proper operation. Tests 




Fig. 95 Fig. 96. 

Figs. 95 and 96. — Standard "T" rails for shallow paving. 

recently made at Purdue University^ upon the resistance of ties, 
recorded in the report of the wood preservation committee of the 
American Railway and Maintenance of Way Association, prove 
that ties follow the laws of insulators in general, but that when 
treated with the chloride of zinc preservative process their ap- 
parent resistance is lowered. Calculated results based upon the 
data of these tests, assuming wet treated ties in wet ballast, 
show values of resistance sufficiently high to prevent serious 
interference with signals. Cases in practical operation have 
been reported, however, in which such interference has been 
present. 

Rails. — In the selection of rails also, steam railroad practice 
has been followed to a great extent, although the weight of rail 
used is, on the average, less with the interurban roads. This is 
possible because of the lighter weight of trains and the absence of 

1 Graduate Thesis, Purdue University, by J. T. Butterfield, 1910, 



TRACK LAYOUT AND CONSTRUCTION 



239 



reciprocating motion. The interurban roads make use of the 
*'T" rail almost exclusively, averaging in weight from 70 to 80 
lb. per yard. In city streets a wide variety of rail sections will 
be found from the ''T" rail to the various shapes and sizes of 
grooved girder rails. The ''T" rail has been rather generally 

Table XXVlll. — Dimensions of Standard "T" Rails in Inches 



Type of rail 



Figure 95 



Figure 96 



Wt. per yard, lb. . . 
Height A 

B 

C 

D 

Width of head E.. . 
Thickness of web F 
Width of base G. . . 



80 


90 


100 


80 


90 


5y8 


^% 


6 


41^16 


5iJ^4 


^H2 


1 


IMe 


1 


1^2 


22 ^^2 


WZ2 


m 


2i^^2 


2^^ 


IKe 


IW^2 


1%6 


l^%2 


13%4 


2>2 


2^f6 


2M 


2K6 


2^{6 


33/ 


9/ 


9/ 


35/ 


9/ 


'^764 


716 


716 


"^764 


%6 


4^^ 


5M 


5K 


4K6 


44%4 



100 

5*^4 

1^^4 

25^^4 

14^4 
22>^2 
%6 
5%4 



objected to by city authorities because of the danger to ve- 
hicular traffic offered by the projecting head of the rail and 
the difficulty in paving close to the rail with standard paving 




Fig. 97 

Heavy service. 

Figs. 97 and 98.— Standard 





K 2 


-— — 1 






H>- 

— ^=s^ 


■f.-Tr> 
r Ma" 












;fc 


-j^jZZ^^^ 


\^y{l 


-A 


1 


6 


1 


1 



Fig. 98 

Light service. 

rails for paved streets. 



blocks. Two sizes of girder rails, 7 in. and 9 in. in height respect 
ively, have come into general use, the latter being preferred from 
the standpoint of ease in paving. 

The American Electric Railway Association in 1910 adopted a 



240 



ELECTRIC RAILWAY ENGINEERING 



standard ''T" rail for city streets for use except where the 
traffic is confined to the railway strip or is so congested that the 
strip is continually used by vehicles. The dimensions of this 
standard for various weights of rails are indicated in Table XXVIII 
which refers to Figs. 95 and 96. 

For the heaviest service, in connection with deep block pave- 
ment, the 7 in. '^T" rail known as ''Section A," Fig. 97, weighing 
100 lb. per yard was adopted. Light service is provided with an 
80 lb. rail shown in Fig. 98 known as ''Section B." 

In heavy city service in connection with deep block pavement 
when vehicular traffic is congested the girder rail, Fig. 99, is used. 
A section similar to Fig. 99 in all respects except that of height, 
which is 7 in. was also adopted by the association in 1913. 

In view of the many difficulties that necessarily have had to be 
overcome in the manufacture of rails to meet the more exacting 







Fig. 99 — Standard girder rail for heavy service. 



demands of heavier trains and higher speeds and because of the 
fact that the selection of proper rails is not a problem of road 
construction alone but of maintenance of way as well, it seems 
desirable to list in detail the more important specifications which 
have been approved by the A. E. R. A. and the American Society 
of Testing Materials. 



TRACK LAYOUT AND CONSTRUCTION 



241 



Specifications for Open Hearth Steel Girder and High "T" Rails 

"The steel shall be made by the open hearth process. 

"Bled ingots, and ingots or blooms which show the effects of injurious 
treatment, shall not be used. 

"A sufficient discard from the top of each ingot shall be made at any 
stage of the manufacture to obtain sound rails. When finished rails 
show piping, they may be cut to shorter lengths until all evidence of this 
is removed. 

"The steel shall conform to either of the following requirements as to 
chemical composition, as specified in the order. 

Table XXIX. — Chemical Properties and Tests of Rails 



Class A 



Class B 



Carbon, per cent. ... 
Manganese, per cent. 

Silicon, per cent 

Phosphorus, per cent 



. 60-0 . 75 

0.60-0.90 

not over . 20 

not over . 04 



. 70-0 . 85 

0.60-0.90 

not over . 20 

not over . 04 



"To determine whether the material conforms to the requirements 
specified in paragraph 4, an analysis shall be made by the manufacturer 
from a test ingot taken during the pouring of each melt. Drillings for 
analysis shall be taken not less than 3^ in. beneath the surface of the test 
ingot. A copy of this analysis shall be given to the purchaser or his 
representative. 

"A check analysis may be made from time to time by the purchaser 
from a test ingot or drillings therefrom furnished by the manufacturer. 

"The test specimen shall be tested on a drop test machine of the type 
recommended by the American Railway Engineering Association. The 
specimen shall be placed head upward on the supports of the machine, 
and shall not break when tested wdth one blow in accordance with the 
following conditions: 



Table XXX. — Physical Properties and Tests of Rails 



Weight and height of rail 



Tempera- 
ture of 

specimen, 
degrees 
Fahr. 



Distance 

between 

supports, 

feet 



Weight 
of tup, 
pounds 



Height of drop 



Class A ! Class B 



Rails weighing over 100 lb. 
per yd. an,d 7 in, in depth. . 

Rails weighing 100 lb. or less 
per yd. or 7 in. or less in 
depth 



60-120 



60-120 



2000 ! 15 



2000 : 13 



12 



10 



16 



242 ELECTRIC RAILWAY ENGINEERING 

"The atmospheric temperature at the time of testing shall be recorded 
in the test report. 

''The testing shall proceed concurrently with the operatioti of the 
works. 

''Three rails, each from the top of one of three ingots from each melt, 
shall be selected by the inspector, and a test specimen shall be taken 
from each of two of these. 

"Drop test specimens shall not be less than 4 or more than 6 ft. in 
length. 

"Two drop tests shall be made from each melt. 

"If the result of the drop test on only one of the two specimens repre- 
senting the rails in a melt, does not conform to the requirements specified 
in Section 7, a retest on a specimen from the third rail selected shall be 
made and this shall govern the acceptance or rejection of the rails from 
that melt. 

"The cold templet of the manufacturer shall conform to the specified 
section as shown in detail on the drawing of the purchaser, and shall at 
all times be maintained perfect. 

"The section of the rail shall conform as accurately as possible to the 
templet, and within the following tolerances: 

"The height shall not vary more than 3^4 in. under nor more than ^2 
over that specified. 

''The overall width of head and tram shall not vary more than 3^ in. 
from that specified. Any variation which would affect the gauge line 
more than }i2 in. will not be allowed. 

"The width of base shall not vary more than 3^ in. under that specified 
for widths less than 6]4 in.; ^q in. under for a width of 63^ in.; and 3^ 
in. under for a width of 7 in. 

"Any variation which would affect the fit of the splice bars will not 
be allowed. 

"The base of the rail shall be at right angles to the web; and the 
convexity shall not exceed 3^2 iii- 

"When necessary on account of the type of track construction, and 
notice to that effect has been given to the manufacturer, special care 
shall be taken to maintain the proper position of the gauge line with 
respect to the outer edge of the base. 

"Unless otherwise specified, the lengths of rails at a temperature of 
60°F. shall be 60 and 62 ft. for those sections in which the weight per 
yard will permit. 

"The lengths shall not vary more than 3^ in. from those specified. 

"Shorter lengths, varying by even feet down to 40 ft. will be accepted 
to the extent of 10 per cent, by weight of the entire order. 

"The weight of the rails per yard as specified in the order shall be 
maintained as nearly as possible after conforming to the requirements 
specified in Section 4. 



TRACK LAYOUT AND CONSTRUCTION 243 

''The total weight of an order shall not vary more than 0.5 per cent, 
from that specified, 

''Payment shall be based on actual weights. 

"Rails on the hotbeds shall be protected from water or snow, and 
shall be carefully manipulated to minimize cold straightening. 

"The distance between the rail supports in the cold straightening proc- 
ess shall not be less than 42 in. except as may be necessary near the ends 
of the rails. The gag shall have rounded corners to avoid injurj^ to the 
rails. 

"Circular holes for Joint bolts, bonds, and tie rods shall be drilled to 
conform to the drawings and dimensions furnished by the purchaser. 

"In Class A rails the tie rod holes ma}^ be punched. 

"The ends shall be milled square laterall}^ and vertically, but the base 
may be undercut ^2 in. 

"Rails shall be smooth on the head, straight in line and surface without 
any twists, waves, or kinks, particular attention being given to having 
the ends without kinks or drop. 

"All burrs or flow caused b}" drilling or sawing shall be carefully 
removed. 

"Rails shall be free from gag marks and other injurious defects of 
cold straightening." 

The composition of the third or conducting rail may be such 
as to result in a much softer and lower resistance rail. Arm- 
strong gives the following anatysis for such rails. 

Table XXXL^ — Axalysis for Third Rails 

Carbon not to exceed . 12 per cent. 

Manganese not to exceed . 40 per cent. 

Sulphur not to exceed 0.05 per cent. 

Phosphorus not to exceed 0. 10 per cent. 

The use of manganese steel for the centers of special w^ork and 
even for complete frogs, switches and curves has been recently 
given a great deal of attention because of its long life. While it 
seems to be the consensus of opinion among railway operators 
that the latter uses of manganese steel are advisable only in 
extreme cases of heavy Tvear, the adoption of replaceable frog 
and switch points of this material is very heartily sanctioned. 

Rails of Steel Alloys. — It may have been inferred alread}^ from 
the chemical specifications set forth in Table XXIX that the 
amounts of various chemicals present in steel rails greatly change 
the physical properties and life of the latter. Carbon, of course, 
increases hardness at the expense of ductility w^hile phosphorus 

^Electric Traction, by A. H. Armstrong. 



244 ELECTRIC RAILWAY ENGINEERING 

makes the rail brittle and of coarse crystalline structure. As 
the safe temperature possible for finishing rails is also lowered 
by the presence of phosphorus the latter must be kept to a 
minimum. 

Some other elements have, however, been added to steel rails 
to good advantage. The difficulty of the problem lies in the 
sacrifice in ductility and low first cost which must be made in 
order to obtain hardness. The addition of about 0.1 per cent, of 
titanium or the use of ferro-titanium tends to make the steel more 
homogeneous and thereby allows the percentage of carbon to be 
increased with no loss of ductility or shock resisting qualities. 
Whether the increased expense of this alloy is warranted remains 
to be determined by longer experience. This treatment can be 
applied to either Bessemer or open hearth processes. 

In particular locations in the track where the rails receive very 
hard wear such as at curves, frogs or crossings, ferro-manganese 
steel has been used to advantage. The addition of from 12 to 
15 per cent, of manganese to the open hearth steel adds greatly 
to its hardness without seriously limiting its ductility. Since this 
steel must be quenched in water when red hot which in turn results 
in much care and time being spent in the straightening process, 
and since this steel cannot be machined or drilled after quenching, 
its first and installation costs are greatly increased. 

Until the so-called Cuban ore, containing about the correct 
percentages of nickel and chromium, was used in the manufacture 
of steel rails, much trouble with broken rails was experienced where 
the nickel-chrome steel was employed. This new ore, requiring 
only a slight addition of nickel in the furnace, has been converted 
into rails during the last few years by both the Bessemer ancj 
open hearth processes. These rails seem to have the desirable 
hardness without corresponding increase of cost. They have not 
been in use long enough, however, to determine what the in- 
creased life and wearing qualities may be. 

Rail Joints. — Aside from the mechanically rigid rail joints 
produced by cast welding, thermit welding and electric welding 
discussed in some detail in Chap. XVII, several other types of 
rail joints in rather more common use should be mentioned. The 
simplest and cheapest joint is of course the four or six bolt fish 
plate clamped on either side of the rail ends. This construction 
allows considerable vertical motion to the ends of the rails as the 
train passes over them, causing the heads to be soon flattened. 



TRACK LAYOUT AND CONSTRUCTION 245 

The rail must therefore be replaced or shortened because of its 
worn condition at the end before it is seriously worn elsewhere. 

The other types of joints most commonly used are the Atlas, 
Continuous and Weber joints, all of which make use of combined 
splice bars and tie plates differing but slightly in design, i.e., they 
all furnish an iron plate between the foot of the rail and the tie, 
which plate is generally notched to receive the spikes in order 
to prevent creeping. The Weber joint makes use of a single 
plate cast in one piece with one of the vertical plates while the 
other joints involve two half plates split longitudinally under the 
center of the rail. 

The use of tie plates is a matter open for discussion. They 
probably increase the life of the ties, especially when rather soft 
wood is used, by preventing chafing between rail and tie, but 
many engineers are not convinced that this gain warrants the 
extra expense. 

Rail joints may be of the '^ suspension" or "supported" type, 
the former having the rail ends between ties, while the latter 
provides a tie directly under the ends of the rails. The former 
seems to be in more general use. In case the Atlas rail joint be 
selected the suspension type must be used, as this joint requires 
transverse bolts through the casting under the rail flanges at the 
end of the rail. 

Both 30 and 60 ft. rail lengths are in use, the former being 
preferred in interurban construction because of less expansion 
troubles therewith and the greater ease of handling the shorter 
length on curves. Where the above features are not objectionable, 
however, the 60 ft. rail has the advantage of fewer joints and 
bonds, thereby reducing slightly the first cost and maintenance 
charges. The shorter rail lengths are meeting with increased 
favor. 

Rail Corrugation. — For several years rails subjected to heavy 
traffic have been found to wear in the form of corrugations which 
may become of such magnitude that they must be ground to a 
depth of 0.06 in. in severe cases in order to remove the irregulari- 
ties. Although several plausible theories have been advanced, the 
cause of this trouble has not been satisfactorily explained for the 
widely varying conditions under which the corrugations are found 
are hardly fulfilled by any one theory. 

For example corrugations are found more often in the following 
cases : 



246 ELECTRIC RAILWAY ENGINEERING 

High girder rails in paved streets. 

Outside rail of long radius curves. 

Rails rigidly supported on concrete foundations. 

One portion of a single rail may be affected while other portions 
of the same rail are free from corrugation. 

Rails corrugated in one section of track are found to wear 
smooth when located elsewhere. 

Time required may vary from 48 hours to several years. 

Reproduced immediately after grinding in some cases and 
eliminated in others. 

Corrugations are absent under the following conditions: 

Practically all steam railroad tracks. 

Nearly all '^T'' rails, especially on interurban road, except 
near stations or where cars are started or stopped under abnormal 
conditions. 

Some of the theories which have been advanced to explain the 
camse of corrugation are: 

Chattering of brake rigging during stop. 

Nosing of wheels transversely across rails. 

Chattering of rolls when rails were rolled. 

Alternate hard and soft spots in composition of rails. 

Cold rolling action of wheels on rails. 

The last theory seems to be the most plausible one offered thus 
far and nearly all conditions of corrugation can be explained 
thereby. This has been outlined in considerable detail by 
Pellissier^ and Gidanski.^ 

The contact area between wheel and rail is so small that the 
pressure may exceed 40,000 lb. per square inch in practice. 
This is very near if not in excess of the elastic limit of the rail. 
It would be safe to say, therefore, that the elastic limit is often 
exceeded with the wheel in motion. Where this takes place it 
would have a tendency to cause the metal to flow slightly until 
the density was increased sufficiently to withstand the force of the 
wheel. The wheel would then tend to ride over the place of high 
density and start the metal to flow just beyond this point. The 
coning of the tread can be shown to aggravate this effect and 
produce the shape of groove which is actually found in practice. 

As grinding the head of the rail is the only satisfactory remedy 

^ ''A New Theory of Rail Corrugation" by G. E. Pellissier, Electric 
Railway Journal, Sept. 30, 1911. 

2 "Rail Corrugation" by C. M. Gidanski, Electric Railway Journal^ 
Dec. 27, 1913. 



TRACK LAYOUT AND CONSTRUCTION 



247 



for this trouble and since the effect will often recur quickly after 
this rather expensive treatment has been applied, it proves to 
be a problem of rather difficult solution. It can be safely said, 
however, to offer a very good argument against the use of too 
rigid a substructure for the support of the rails. 

Roadbed Construction. — Whereas the interurban roadbed con- 
sists merely of a natural sub-soil or fill, well drained with side 




:<l■>;;^;^;:■v<J:^;^v:^?^::T^•^^^S^;.vvV■•:t>'•.•■;.•^^•;v.:■^ 




*?•."•■"■■•:•■>.•'■•• •T>" 



2 Loam 
i'^Washed Pebbles 



\Portiau 



d Goucrete 
1-3-7 



Fig. 100. — Standard track construction, Cincinnati, Ohio. 

ditches and covered with gravel or crushed rock ballast to a depth 
of from 6 to 18 in. under the ties, the problem of roadbed construc- 
tion in city streets is a more difficult one. A trench is first ex- 
cavated slightly greater in width than the length of the ties and of 
a depth depending upon the type of foundation to be used. Al- 
though the old method of excavating a transverse trench for each 
tie is now practically obsolete, many companies are keeping 



5.33 Between Track Centers 




^1^^ s'bijfessed B Jl ock Paljcmentl l 



\^mm O^C^ncrete \gg^j^ 



5 Concrete Slab for Pavement 

e'Tile Drain 



;^:fl^::<C^ Cinders 



Fig. 101, — Standard track construction, Cleveland, Ohio. 

lengths of ties to a minimum and reducing the foundations and 
ballast as much as possible in order to decrease excavation costs. 
The use of the longitudinal concrete beam construction under the 
rails is little in favor at present. 

Although most engineers will agree that the roadbed should be 
well drained, comparatively few roads are going to the expense of 
installing longitudinal tile drains under the ballast of single 
track or between the tracks of a double track road. Cincinnati, 



248 



ELECTRIC RAILWAY ENGINEERING 



Kansas City, Cleveland, Seattle and some of the other large 
cities claim good results from such tile construction. Where 
installed, it has been found desirable to use bell and spigot sewer 
tile rather than the soft agricultural drain tile. The latter is 
found to crush and fill up too easily under heavy traffic conditions. 
Sections taken through standard roadbeds using drains are seen 
in Figs. 100, 101 and 102. 



m" 



i Toothing stone I I 

Vl5 



4 8>6' 



Medina Sandstone Paving 



_ 5 To G a ge Line 
H Crown 



S P^-^Screw Spilies 













m" Crushed stone for Tamping 



Coarse Sand 



J 



4 Farm Tile • 



X. 



m 



Hemlock Trough — T^„"_^ 
I 

Fig. 102. — Standard track construction, Buffalo, N. Y. 

Opinions of expert railway engineers differ as to whether the 
roadbed should be perfectly rigid or somewhat flexible. With the 
former construction the rolling stock is believed to suffer to a 
greater extent and rail corrugation seems to be more marked. It 
is also difficult to construct where traffic cannot be readily di- 
verted from the track. With the flexible construction, ties have 
shorter life and rails are more readily thrown out of alignment. 



/•Asphalt 



1 to 1]4 of Sand 




Crushed Rock or Gravel 



Fig. 103. — Standard track construction, Minneapolis, Minn. 

The simplest form of flexible construction which is not unlike that 
common in interurban practice, with the exception of pavement, is 
indicated in Fig. 103, a construction which has been adopted as 
standard in Minneapolis. 

In the more elaborate sections shown in Figs. 100,101 and 102 a 
concrete sub-base is first laid in the excavation, followed by a 
cushion of sand for the ties and pavement. In the Cleveland 



TRACK LAYOUT AND CONSTRUCTION 



249 



construction it will be noted that steel ties have been grouted into 
the concrete sub-base without a cushion, while in Milwaukee 
standard practice with macadam pavement calls for a layer 
of concrete over layers of crushed stone and coarse rock bal- 
last. The use of screw spikes should be noted in the Cincinnati 
track as well as the knee braces which replace the tie rods with 
the girder rails. 

The use of tie rods to prevent the overturning of high girder 
rails is difficult with heavy block paving. In some installations 
these rods of round section are placed low on the rail and therefore 
under the paving blocks, while in other cities a thin flat rod is used 
which will fit in the joints between paving blocks as in Fig. 102. 
In at least one city interference with the blocks has been avoided 
and at the same time the desirable high connection on the rail 



lO' Between Track Centers 




No. 2 Medium 
Gr.Stone 

No. 4 Coarse 
Gr.Stone 



Fig. 104. — Standard track construction, Milwaukee, Wis. 



has been maintained by an offset rod of round section passing 
under the paving blocks. 

Pavement. — The railway company is usually required to install 
and maintain the pavement between tracks and for a distance of 
2 ft. or more outside. If paving blocks are used with anything 
but a 9 in. girder rail a special block must be secured to fit the 
rail and provide a groove inside the rail sufficient to allow the 
wheel flange to pass without forming a dangerous rut for vehicular 
traffic. Such grooves are rapidly worn away by the latter traffic 
and the railway company endeavors, therefore, so to design the 
track and paving that the vehicles will not be attracted thereto. 
This policy will often aid in making schedule time in city streets 
as well. With the grooved girder rail the groove provides room 
for the flange. In many cities the city authorities specify the 
type of pavement which must be installed between and for a short 
distance upon either side of the tracks. The most common forms 



250 ELECTRIC RAILWAY ENGINEERING 

are brick, stone blocks and wooden blocks. Asphalt and con- 
crete have been used to a slight extent. The difficulty with 
these types lies in the fact that frequent removal for repairs 
is not only accompanied with much labor and expense but there is 
no salvage of material for replacement as there is with practically 
all types of block pavement. 

Blocks, however, have the disadvantage that it is practically 
impossible to make such pavement watertight. If not water- 
tight the life of ties and wooden blocks is greatly impaired and the 
freezing of water under and between blocks is very likely to cause 
bulging and cracking of the surface of the pavement. This latter 
difficulty has been overcome in some instances by setting the 
blocks in cement grouting. 

Creosoted wooden block pavement with a tar binder has found 
much favor during the last few years. It is practically waterproof 
and of long life while not difficult to install and replace. It 
offers a less slippery and harsh surface for the feet of horses and is 
readily fitted into shallow rails and round special work. In 
some instances where insufficient expansion joints have been 
left to care for the rather great expansion which takes place in hot 
weather, difficulties with upheaval of the paved surface have 
been met, but properly installed wooden blocks have produced a 
cheap, efficient .and long-lived pavement in many large cities even 
when subjected to heavy vehicular traffic. 

Special Work. — Special work, which is the term given to track 
switches, frogs, crossings and, indeed, practically all track 
construction not made up of standard rails, is usually subjected 
to relatively heavy traffic and a correspondingly great amount of 
wear. This special work is sometimes made up of sections of 
rails set in steel castings or it may be entirely a steel casting. 
Recent practice tends toward the use of manganese steel for such 
castings where the expense seems warranted while in other cases 
manganese steel " points" are inserted in the casting at the proper 
location to receive the greatest amount of wear. Much difference 
of opinion is expressed as to whether these inserts should be made 
removable or permanently installed. If the former practice is 
adopted it is very difficult to replace satisfactorily the worn out 
insert as the remainder of the casting is usually badly worn also. 
Even with manganese steel points, however, some saving is prob- 
ably possible if the construction of the special work is so designed 
as to permit of their replacement. 

Considerable advance has been made during the last few years 



TRACK LAYOUT AND CONSTRUCTION 
Estimated Cost op Roadbed Construction 



251 



Labor Material 



Total 



diam 



Clearing and Grubbing. 

68 acres at S45 

Grading. 

Solid rock 8000 yd. at SO. 75 

Loose rock 35,000 yd. at S0.37 

Earth, 716,000 j'd. at SO. 145 

Culverts. 

150 Culverts varying from 18" to 60' 
Total 4573'. 

Hauling and placing 

End walls 1300 yd. at S8 

Timber Bridges. 

41 Pile bridges, 4752 lin. ft. at S8.80 

1 Frame bent bridge, 800 lin. ft. at SI 0.25 . 
Steel Bridges. 

9 Steel spans ranging from 30' to 130' 
700,520 lb. erect, at 43^ cts. 

Concrete piers, 2300 3^d. at S7.20 

Deck, 2300 yd. at S2.50 

Track. 

Rail 80 lb. 33', 8431.7 tons at S33.515. . . . 

Angle bars, 21,690 prs. at 0.86 

Track bolts, 86,762 at 0.04 

Track spikes, 2010 kegs at S5.60 

Bonds, 21,160 at 0.60 

Cross bounds, 67 total 

Track ties, 169,860 at 0.65 

Switches compl., 18 at S150 

Labor 

Ballast. 

Local gravel or lime rock 

Fencing (TFiVe). 

26,900 rd 

Miscellaneous. 

Railroad crossings at S300 

Highway and private crossings at S47 .... 
. Signs 



S3, 060 

6,000 

12,950 

103,820 



9,420 



995 
10,400 

14,000 
2,730 



27,818 
5,470 



3,502 25,395 



8,280 
675 



3,196 



8,280 
1,300 

282,588 
18,653 

3,471 
11,256 

9,500 



110,409 
2,700 



$3,060 



122,770 



20,815 



50,018 



47,432 



600 



26,548 
130,000 



Grand total ' S866,748 



5,380 


11,112 


200 


1,000 


1,150 


4,490 


100 


300 



; 468,921 

i 

130,000 
16,492 



7,240 



in the standardization of special work, particularly by the Ameri- 
can Electric Railway Association. This is of advantage not only 
to manufacturers, who may decrease materially their patterns and 
tools, but to operating companies because of increased ability to 



252 ELECTRIC RAILWAY ENGINEERING 

obtain prompt shipments and order and replace parts intelli- 
gently with little chance of error. To this end the switch 
laid out upon a 100 ft. radius curve has become the most popular 
standard, while frogs and mates may be readily specified by num- 
ber from a comparatively small standard list, the number indi- 
cating a distinct casting with certain field dimensions. These 
standards are clearly set forth in the manual of the association 
named. 

Estimates. — Whereas the cost of materials varies greatly in 
different portions of the country, estimates or actual costs of 
construction must be taken with a great deal of caution. They 
seem to be of suflacient value as a study of approximate relative 
values, however, to warrant listing herein. Such an estimate 
covering the construction for an interurban line 63 miles in length 
in the South will therefore be found on page 251. 

The estimate represents an expenditure of $13,700 per mile for 
roadbed and track exclusive of engineer's fee and contractor's 
profit. It is interesting to note that of the above total 37.8 per 
cent, is labor and 62.2 per cent, material. 



CHAPTER XXI 

CARS 

Car Selection. — Notwithstanding the fact that electric trac- 
tion has been developed within a comparatively few years, cars 
which are now operated upon the various city and interurban 
lines of the country range from the 20 ft. single truck made over 
horse cars to the 70 ft. magnificent limited double truck parlor 
cars weighing from 50 to 70 tons and provided with all the con- 
veniences of the Pullman coach. With this array of possible 
rolling stock to choose from the problem of car selection for a 
proposed road or for additions to present equipment on city 
or interurban systems is a difficult matter. Too little attention 
has been given to this problem in the past, the questions of suffi- 
cient seating capacity and finish often being the principal con- 
siderations in the selection of cars. These factors are of course 
of prime importance, for the public patronage is not only depend- 
ent upon the ability to obtain a seat in a car, especially upon a 
long journey, but also to a surprising extent upon the appoint- 
ments of the cars with respect to personal convenience. Track 
and street conditions often impose limits on the dimensions of 
cars which may be used on a given road. The class of service in 
which the car is to be used, whether city, suburban, or interurban, 
defines to a certain extent the type of car. In city service local 
conditions, such as climate, topography, size of city, kind and 
location of industrial works, volume of vehicular traffic, dis- 
tribution of population and social characteristics of the people, 
enter more or less directly into the problem of car selection and 
influence the choice of type. The main questions in the problem 
however, are: 

1. Method of fare collection. 

2. Location and arrangement of entrances and exits. 

3. Seating and standing capacity. 

4. Dimensions and weight of car. 
These questions are largely determined by: 

1. Average length of ride per passenger. 

2. Average number of passengers per car mile. 

253 



254 ELECTRIC RAILWAY ENGINEERING 

3. Average number of stops per mile. 

4. Maximum safety in operation. 

5. Cost of operation and maintenance. 

In the selection of cars for interurban service some of the more 
important points to be considered are: 

1. Nature of traffic, whether passenger, freight or express. 

2. Length of road. 

3. Social conditions. 

4. Schedule speed. 

5. Condition of roadbed and structures. 

6. Convenience of patrons. 

7. Nature of competition if competition exists. 

8. Whether or not the road enters the cities along its route over 
private right-of-way or over city streets. 

At the present time careful engineers are studying the problems 
of car selection and design as they have never been studied before 
and much emphasis is being placed on the economic ratios; 
''weight of car per seat," ''weight of car per square foot of floor 
area," and "weight of car per foot of car length." 

Car Bodies. — With the gradual increase in speed of cars there 
came an increasing number of wrecks which soon proved the 
average car construction to be unsuitable for withstanding severe 
strains and thereby protecting passengers to some extent from 
injury in case of collision. Then came a period of marked in- 
crease in the weight of cars with correspondingly increased 
capacity of car equipment not only, but of feeders, substa- 
tion and power station capacity as well. Quite recently, how- 
ever, another reaction has taken place, for it has been found that 
the desired strength to resist the abnormal forces in service may 
be obtained by proper design with even less weight. This ap- 
parently paradoxical condition is partly due to the fact that the 
use of steel in place of wood will give greater strength with less 
weight and also for the reason that a car may be constructed 
as a double truss, the side frames acting as one truss to transfer 
the load to the bolsters and the bolsters in turn acting as trans- 
verse trusses between car sills and truck support. For steel 
frame construction see Fig. 105. 

The better types of recently designed car bodies are either 
all steel or partly steel. The great advances made within the 
past few years in the art of sheet metal working have made it 
possible to construct pressed steel shapes cheaply in almost any 



CARS 



255 



form desired. These shapes are much used in modern car body 
construction. All steel cars are fireproof and in case of wreck 
they do not telescope readily, nor do they break up into dangerous 
splinters. The car floors used in these cars are of the so-called 
''monolithic type" and are made by spreading either a plain or 
reinforced cement on a base of galvanized iron and special shapes. 
The monitor tj^pe roof, Fig. 113, is rapidly being replaced 
by the arch type, Fig. 114, which is stronger, lighter and easier 




Fig. 105. — Steel frame car construction. 



to construct and gives greater headroom for a given height of 



car. 



Metal and composition ceilings are being used instead of the 
wood veneers used a few years ago. These new ceilings are fire- 
proof and do not warp or shrink. 

The desirable reductions possible in cost of power, car repairs, 
track repairs, fixed charges on power plant and distribution sys- 
tem with decrease in weight of cars are very clearly pointed out 
in a paper by M. V. Ayers, then electrical engineer of the Boston 
& Worcester Street Railway before the American Association in 
1909. In this paper formulas are developed for the foregoing 
cost reductions and suggestions are given for possible decrease 



256 ELECTRIC RAILWAY ENGINEERING 

in weight of cars without curtailment of strength. Aside from 
the above truss design and steel underframing, the use of 
aluminum and cast bronzes in place of iron, soft woods in many 
places instead of hard woods and the reduction in the weights of 
motors with forced ventilation are mentioned. 

Other marked advances are the standardization by the above- 
named association of the heights of couplers, platforms, bumpers 
and many other construction details of both city and interurban 
cars,^ and the use of corrugated iron buffers or ''anti-climbers'' 
to prevent telescoping of platforms in case of collision. Such 
telescoping was the cause of much damage in several recent and 
very serious interurban wrecks in the Middle West. 

Trucks. — The truck primarily consists of two pairs of wheels 
and axles upon whose journals a steel framework is supported by 
means of combined helical and elliptical springs. This framework 
serves to take the weight of the car body not only, but also to 
form a support for the brake rigging and a portion of the weight 
of the motors. Since the axles are held in a position parallel 
to each other by the fixed journal boxes the distance between 
axles cannot exceed a certain value, generally 7 ft. 6 in., be- 
cause of difficulties in following curves of short radius in the 
track. With this limitation and with the further fact dem- 
onstrated by practice that single truck cars tend to rock badly 
in the direction of motion, the length of single truck car bodies 
must necessarily be limited to from 22 to 25 ft. overall. For 
the longer cars two trucks with king pins located as near the 
ends of the car as possible without interfering with vestibule 
supports must be used. 

With either type of truck the motors are suspended with two 
babbitted boxes, cast in one side of the motor frame, bearing 
on the car axle, and the opposite side of the motor is hung by 
means of a flexible link from the truck frame. The so-called 
"nose" suspension provides but one support between motor 
and frame, while the "yoke'' suspension, as the name im- 
plies furnishes two such connections. With these suspensions 
the motor is permitted to swing slightly about the car axle as a 
center as the car passes over irregularities in the track, thus keep* 
ing the pinion on the motor shaft at all times in mesh with the 
gear on the car axle. 

Trucks are provided with car wheels ranging from 22 to 37 in. 

1 A. E. R. A. Engineering Manual, 1914. 



CARS 



257 



in diameter, the larger sizes being generally used in heavy inter- 
urban traction. Wheels are constructed of cast iron with chilled 
treads, cast steel, or a combination of cast iron centers with steel 
rims. The latter t3'pe has now been largely replaced on inter- 
urban roads by the cast steel wheel, as some difficulties were 
encountered due to the steel rims working loose in service. 
Wheels may be re-turned four or five times before scrapping is 
necessar}', a reduction of from M to 1}^ in. in diameter being 
possible before wheels must be discarded. Steel wheels will 
range from four to five times the mileage of cast iron wheels and 
the latter are considered unsafe above 30 m.p.h. WTieels vary- 
ing as much as 2 in. in diameter have been successfully used on 
different axles of the same car, although those on the same axle 




Fig. 106. — JM. C. B. truck; Baldwin Locomotive •Works. 

must be of the same diameter. The wheels are forced on 
the axles under hj^draulic pressures of from 25 to 50 tons, de- 
pending upon the tj^pe of wheel and size of axles. 

Car axles are turned from cold rolled steel and vary in diameter 
from 4 in. with the smallest motors up to 7 in. with 200 and 250 
hp. motors in heavy service. 

Formerly it was general practice to lubricate truck journals 
by means of cotton waste, soaked in grease, packed in the journal 
box. While this method is still used to a limited extent, the best 
practice at present is following the lines laid down years ago by 
the steam railways, namely, the use of oil soaked woolen waste, 
packed in a large journal box and surrounding the part of the 
journal not covered by the ''brass." 

Trucks are provided with side bearing plates upon which 
similar plates on the under side of the car may rest when the 
latter is unequally loaded or upon curves to prevent too great 
tilting of the car. 

17 



258 



ELECTRIC RAILWAY ENGINEERING 



Fig. 106 shows the M. C. B. (Master Car Builders) type of 
truck. This truck is patterned after the type used under steam 
railway coaches and has found considerable use in electric 
railway practice. 

-The ''rq^aximum traction'' truck, Fig. 107, is being used to a 
wide extent under modern light weight, low platform cars. 
It is particularly well adapted to the form of construction used 
in the ^'stepless" center entrance cars. Fig. 115. 

Motor Equipment. — The question of whether a two or four 
motor equipment should be installed must receive careful 




Fig. 107. — Maximum traction trucks. The J, G. Brill Co. 

thought. Previous chapters have described the method of 
determining the total power required for the car, but whether 
this should be supplied by two or four motors is quite another 
problem. With single truck and maximum traction truck cars 
two motors only are possible. In the case of double standard 
truck cars, four motor equipment is probably most commonly 
found, although many roads are operating with but one motor 
per truck. Tests which have been made with the same car 
equipped in both ways disclose the fact that under certain con- 
ditions, such as heavy grades, large number of stops per mile, 
and severe climatic conditions, the four motor equipment will 
require less power for the same schedule. This is largely due 
to the distribution of torque over the larger number of driving 
wheels. This torque distribution as well as the reserve capacity 
over that called for by the theoretical calculations, especially 
under the abnormal conditions of snow fighting and making up 
lost time, are usually considered of tangible monetary value by 
traction managers. 



CARS 259 

For these reasons the four motor equipment has generally 
found favor where heavy cars are used. While the control 
equipment and car wiring are slightly more complicated with 
the four motor equipment, the ability to use two motors, or- 
dinaril}^ with one on each truck, in case of failure of one or more 
of the other set is worthy of consideration. In short, the con- 
tinuity of service and maintenance of schedule speed must be 
thought of as well as first cost of equipment and operating 
expense. 

Lighting. — The very unsatisfactory- nature of car lighting at 
the present time, especially upon interurban roads, has been 
commented upon in a previous chapter. The reason for this, 
in the face of public criticism on roads where everything else is 
done for the convenience and comfort of the passengers, is difficult 
to understand. The present method of lighting is that of using 
several series of five incandescent lamps each protected by fuses 
and connected directty between the trolley and ground so that 
the lights will not be extinguished when the circuit breaker 
opens. Several clusters are distributed throughout the hood of 
the car and often a light is placed over each seat. The incandes- 
cent headlight, if one be used, may be lighted in place of the 
vestibule light on the front end of the car b}^ means of a snap 
switch. All the lights are, of course, dependent upon trolley 
voltage, which has been previousl}^ shown to vary over a wide 
range, with more than proportional variations in light intensity. 
A lighting system independent of trolley voltage must sooner or 
later replace this unsatisfactory^ method of car lighting. 

In the high voltage direct current systems the lighting circuit 
usually receives its energj- from a djmamotor or motor generator 
set, which transforms the high trollej^ voltage down to 600 volts 
for the air compressor, lighting and control circuits. Where 
alternating current systems are used, the lights are usually fed 
from a small special transformer. 

The use of tungsten lamps is a distinct advance over the old 
carbon filament lamps, as they are much more efficient and are 
not affected to as great an extent by voltage variations. 

The fact that low voltage tungsten lamps are particularly well 
adapted to railwaj^ work has made possible a new type of light- 
ing system that is being tried out with very gratifying results so 
far by a well-known interurban road^ which has to meet severe 

^ Michigan United Traction Co., see Electric Railway Journal^ July 18, 
1914. 



260 ELECTRIC RAILWAY ENGINEERING 

competition from steam roads. In this system the lamps are 
lighted from a storage battery. The 30 volt system, which has 
practically become the standard in steam coach lighting systems, 
is used. The batteries are charged by means of a motor generator 
set, the charging being done in the day time. The motor gen- 
erator set is of such design that its terminal voltage is not greatly 
affected by variations in the line voltage and therefore compli- 
cated voltage regulators are not required. 

Arc headlights are often used on interurban lines with some 
provision for operation upon city streets such as a gauze shade, 
reduced voltage, polarity reversal in the case of the magnetite 
arc, or the substitution of an incandescent lamp. These head- 
lights require from 4 to 43-^ amp. at 550 volts, of which more than 
80 per cent, is wasted in external resistance. At present high 
power tungsten lamps equipped with good reflectors are being 
used to a considerable extent in headlight service. 

Car Heating and Ventilation. — At present four types of car 
heating systems are available, namely: electric, hot water, hot 
air, coal stoves. First cost, cost of operation and maintenance, 
convenience in handling, safety, type of car, severity of climate, 
and nature of run are some of the factors which affect the choice 
of a heating system. All-steel cars usually require from 20 to 30 
per cent, more heat than do wooden cars operating under similar 
conditions. The use of double window sashes in severe weather 
reduces the amount of heat necessary to keep a car in comfort- 
able condition. Interurban and other ''long haul" cars must be 
heated differently than the city car where the length of ride is 
usually short and passengers do not remove their outer wraps. 

Many city cars and some of the smaller interurban cars are 
heated by means of electric heaters provided with switches lo- 
cated in the vestibule which will permit several degrees of heat. 
Heater regulation (1) by the car crew, (2) by the dispatcher, (3) 
by automatic means has been tried out. While in first cost it 
is most expensive, the automatic method of control, in which a 
thermostat regulator controls the manipulation of the heater con- 
trol switch, seems to give the best satisfaction. Electric heaters 
should be so placed that the clothing of passengers cannot come 
into contact with any part of the heater or screen the heater so 
that currents of air cannot pass freely. The Electric system of 
car heating is clean, convenient and easily maintained, but is 
costly to operate. The problem of car heating, especially upon 



CARS 261 

long exposed runs at high speed in the coldest weather, is a serious 
one, a car requiring from 10 to 30 amp. at 550 volts for such ser- 
vice. One large city railway system in particular, although able 
to supply the demands of summer traffic with existing power sta- 
tion equipment, was forced to install additional apparatus and 
enlarge its station in order to meet the car heating demand in 
winter. 

Ventilation, with the electric system, is secured in several ways. 
One method employs a small motor-driven blower which draws 



Fig. 108. — Pantograph and wheel trolleys. 

outside air through a duct from some place near the roof and forces 
it through other ducts which have outlets near the heaters. The 
foul air ascends and passes out at the ceiling through special 
ventilators. In another method the ventilators are so shaped that 
they act as " ejectors" w^hen the car is in motion and draw the foul 
air out of the car, fresh air being supplied through holes in the 
sides of the car near the heaters. In manj^ cit}^ cars the doors are 
the only means of ventilation in the winter time. However, 
pubhc opinion is becoming rather exacting on the point of ven- 
tilation and the better types of cars are being equipped with venti- 
lating systems. A ventilating system to be effective must be 
able to supply from 600 to 800 cu. ft. of air per passenger per hour. 
In m_any of the newer types of cars a special type of hot air 
heater is being used. A motor-driven blower drawls fresh air 
from the outside of the car and forces it over the heating surface 
of an enclosed stove or hot air heater. The air is then either dis- 
charged directly into the car or distributed by means of ducts to 
various parts of the car. The foul air escapes through ceiling 
ventilators. These heaters usually burn hard coal. They re- 
quire very little attention and are very economical. 



262 



ELECTRIC RAILWAY ENGINEERING 



The coal stove is practically obsolete as a means of car heating. 

Interurban companies, and especially those operating single- 
end cars, have adopted the hot water heating system almost ex- 
clusively, the heater being located in one end of the car, prefer- 
ably in the baggage compartment or motorman's cab. This 
system has the double advantage of low cost of operation and 
more even distribution of heat in the car, this being accomplished 
by means of pipes encircling the car near the floor as in the case 
of the cars of steam railroads. Ventilation is secured by methods 
similar to those described under electric heating. 

Current Collection. — ^Little change has been made in the over- 
head trolley since the earliest days of electric traction, its opera- 




FiG. 109. — Near view of pantograph trolley. 



tion being entirely satisfactory except for the very highest speeds 
or for the collection of very heavy currents. Large trolley wheels 
are used for high speed service and each road has a particular 
composition for the wheel casting which it believes to be best for 
local conditions. Wheels should run from 5000 to 10,000 miles 
before replacement is necessary. 

The pantograph bow collector is coming into general use in high 
voltage high speed service. Such a device is illustrated upon a car 
in Fig. 108. It is raised to the wire by air pressure, the control- 
ling valve being in the motorman's cab. With this type of col- 
lector the alignment of the trolley wire is not important, as the 
collector is often 2 ft. or more in length and any transverse move- 



CARS 



263 



ment prevents local wearing of the collector. A near view of the 
pantograph collector built by the General Electric Company for 
the electric locomotives of the Butte, Anaconda & Pacific Rail- 
way is shown in Fig. 109. 

The third rail shoe for collecting heavy currents from the third 
rail mounted beside the running rails has been referred to previ- 



i % 





Fig. 110. — Third rail shoe and mounti 



ously. A view of one of the many types may be found in Fig. 110. 
Some difficulty has been encountered in the past with this con- 
struction in winter, for if sleet be allowed to form on the rail the 
shoe tends to ride on the sleet and a poor contact with much arc- 
ing results. Various methods have been devised to overcome this 
difficulty with more or less success. Those most used are a steel 



264 ELECTRIC RAILWAY ENGINEERING 

brush or scraper placed ahead of the shoe and the sprinkhng of the 
third rail with brine. 

Car Wiring. — A great deal of laxity has existed in the past in 
regard to car wiring and many accidents and fires have resulted 
in consequence. As the Underwriter's Code does not rigidly 
apply since cars are not insured, the tendency has been to use 
little care in running the wires under the car. Rubber covered 
wire is of course used, but it is customary to group all the wires 
together in one or two cables in a length of canvas hose hung from 
the car sills and extending from motors to controllers. The 
cable extending from the trolley base is supported on the top of 
the car roof by means of brass clips and is carried either into the 
car vestibule to the circuit breaker with only the insulation of the 
wire or, in the case of master control, it is carried down one of the 
corner posts of the car in moulding. 

Recently the Fire Underwriters^ have drawn up a code of rules 
for car wiring and many improvements have resulted therefrom. 
Asbestos lined conduit is now often laid under the seats of the car 
for the installation of cables, while in the better types of construc- 
tion, iron conduit is . installed as in building wiring. Present 
practice also involves the use of asbestos lumber or galvanized 
iron protection between wiring and wooden car frames, especially 
over the rheostats. Car wiring diagrams will be considered under 
''Types of Control," Chap. XXIII. 

Special Types of Cars. — The preceding discussion applies to all 
types of cars. The special features of cars designed for a particu- 
lar service will be outlined below. 

Pay as You Enter Cars. — The introduction of this type of car 
a few years ago practically revolutionized the construction of cars 
intended for city, suburban and light interurban service. Briefly 
stated, the advantages of the pay as you enter system are as 
follows : 

1. The number of platform accidents is greatly reduced. 

2. The conductor can .collect all fares. 

3. Passengers within the car are not disturbed by the con- 
ductor walking back and forth, and out-going passengers are 
not blocked by in-coming passengers. 

4. The conductor has better supervision over the car. 

An apparent disadvantage is the increased length of stop, but 
this has not proved to be serious as the platforms in this type of 
1 National Electric Code, 1913. 



CARS 



265 



car are very large and when this platform is filled the car is started. 
The fares are paid before the passengers enter the car but during 
the period the car is in motion. This procedure, together with 
the time saved by the conductor being in a position to start the 



6igii,"Pleft»« pay as you get on 




Fig. 111. — Plan of pay-as-you-enter car. 

car promptly, has permitted the same schedule to be maintained 
in several cities with less cars when this type of car has been 
adopted. Views of cars equipped with prepayment devices 




Fig. 112. — Platform of pioneer pay-as-you-enter car. 

will be found in Figs. Ill and 112. These cars are frequently 
designed for single end operation. 

The prepayment plan of fare collection may, of course, be used 
with an}^ t^^pe of car. However, in order to make the best pos- 
sible use of the advantages offered by the prepayment system, the 



266 



ELECTRIC RAILWAY ENGINEERING 



following devices and modifications in car construction were 
introduced: 

1 . Means for separating the in-coming and out-going passengers. 

2. Large platforms or vestibules with unobstructed openings 
into the car body. 

3. Means for controlling the doors. 

City Cars. — In the smaller cities where traffic is not particu- 
larly heavy, the 20 ft. single truck car with longitudinal seats is 
still used. The corresponding summer equipment would be a 
20 ft., 10- bench, single truck car with running board. Officials 
differ as to the advisability of maintaining a double motor equip- 
ment, and many of the smaller roads shift the equipment twice a 




Fig. 113. — Monitor roof type city car. 



year from one type of car to the other. With single trucks this 
involves considerable labor, but if double trucks be used the 
trucks complete with motors can be changed with little trouble. 
Where summer traffic is heavy, especially to summer resorts, the 
35 ft., 15- bench, double truck open cars or small trailer cars are 
used. 

In the large cities the convertible or semi-convertible double 
truck cars. Fig. 113, with either transverse seats throughout or a 
combination of transverse and longitudinal seats, are still being 
used, although many of them have been equipped with the various 
prepayment devices. Fig. 114 shows a typical modern car of the 
same general design. These cars are used throughout the year. 
This avoids duplication of equipment and the dangers incident 
to the operation of the running board type of car in congested 



CARS 



267 



districts. Cars with transverse seats are much more comfortable, 
especially for long rides, but they do not permit rapid ingress and 
egress, nor do they provide the standing room for a given size of 
car that the longitudinal seats furnish. The combination of both 
types of seats for long cars, with the section of transverse seats in 




Fig. 114. — Arch roof type city car. The J. G. Brill Co. 

the center of the car, permits the long haul passengers to ride in 
comfort and yet furnishes more readily accessible seats and stand- 
ing room for the local traffic. 

It will be noted that the newer type of car has tightly closed, 
folding doors, folding steps, enclosed hand grips, marked open- 




FiG. 115. — Stepless center-entrance car. Kuhlman Car Co. 

ings, shielded drawbar, and in general offers no opportunity for 
careless passengers to hang on outside of the car. The doors are 
operated either by compressed air or manually by means of a 
system of levers, and are always closed before the car starts. The 
bulkheads or partitions which separate the platform from the 
main part of the car body are often eliminated in modern cars. 
By so doing greater capacity is secured and there is less ob- 
struction to the entrances and exits. Pipe railings as indicated 
in Fig. 112 divide the in-coming from the out-going passengers. 



268 



ELECTRIC RAILWAY ENGINEERING 



Most of these special features are found on all new cars of all 
types intended for city service. 

The ''stepless" center entrance car, Fig. 115, introduced in 
New York City a few years ago, is becoming an extremely popu- 




FiG. 116.— Near-side car. The J. G. Brill Co. 

lar type of car for service in large cities. These cars are found in 
various modifications. The body is mounted on low wheeled 
maximum traction trucks and the entrance is only a low step 
above the street level. A couple of low steps or one step and an in- 
cline, or "ramp," completes the passageway from the entrance 
platform or "well'' to the car deck proper. These cars can be 
loaded and unloaded very quickly and because of the absence of 



%i5 


j|^r>?E:'w -voiJKtis: |'-' ■',''■' 


1 

tT 


Fij^i]uv«r.A.V!B cct.^^f^^^B^^^^^HKKM^M 



Fig. 117.— Double deck car. The J. 



G. Brill Co. 

The car shown seats 



end platforms have great seating capacity. 
51 passengers. 

The "near-side" car, Fig. 116, is being used to an increasing 
extent, particularly for one man operation. In the larger cars, 
both conductor and motorman are in the front end. The front 
doors are used in service, the rear door being an emergency exit. 



CARS 



269 



All doors are controlled by the motorman and are either of the 
manual or power operated type. The car is particularly well 
adapted for one man operation on lines which handle light traffic. 
Only one stop per block is required even when the cross street 
traffic is heavy, because the car stops on the "near side" of a 
street intersection and loads from the sidewalk line. Plat- 



^^^^Hp^HHHHiHHi^^Hil^^^^H|^^H 


liiipf iri" 

> 


= ■" i ii 


iiiiiinii 11 

—ji 



Fig. 118. — California type car. American Car Co. 



form accidents are reduced to the minimum and the number of 
collisions with vehicles on intersecting streets are greatly reduced 
when this type of car is used. 

Several companies operating in large cities have again intro- 
duced types of double-deck cars, Fig. 117. The use of a construc- 
tion similar to that of the low center entrance car has eliminated 
part of the objections that were formerly urged against this type 
of car. As these cars will seat a very large number of passengers, 
they are particularly well adapted to the carrying of large masses 
of passengers such as must be handled at certain periods of the 
day in the vicinity of large industrial works. 

The California type of car, Fig. 118, is well adapted for use on 
roads operating in warm and mild climates. 

Suburban Cars. — This service in large cities is maintained with 
the semi-convertible and stepless double truck type of cars. The 
car bodies are usually larger and the motor geared for higher 
speeds than are used for city service. 

Open running board cars are used much more in the East than 
in the Middle West for suburban service. Such a car, 42 ft. 6 in. 
in length and weighing 13 tons without electrical equipment, is 
shown in Fig. 119. 



270 



ELECTRIC RAILWAY ENGINEERING 



Interurban Cars. — Cars which have been developed for inter- 
urban service, which has recently grown so rapidly, particularly 
in the Middle West, are patterned after the steam railroad 
coaches. They often reach lengths of 68 ft. and weights of 50 




Fig. 119. — Open running board car. 

tons. These cars have transverse seats and are divided into four 
compartments, for motorman's cab, baggage, smoking and main 
passenger service respectively. This design often precludes 




Fig. 120. — Plan of interurban car. 

double end operation. A plan view of such a car may be seen 
in Fig. 120, while a similar car designed as a sleeper and oper- 
ated upon the Illinois Traction Company's lines between St. Louis 
and Peoria, 111., is illustrated in the plan view of Fig. 121. 




Fig. 121. — Plan of sleeping car. 

The better classes of interurban cars now being built are of all- 
steel construction. A typical all-steel car embodying all of the 
latest refinements in car design is illustrated in Fig. 122. 



CARS 



271 



A light, low Vv'heeled center entrance car somewhat similar to 
Fig. 115 has been tried out in interm-ban service by one interur- 
ban railway company^ operating a short road which enters a large 
city over the tracks of the city railway system. No difficulty has 




Fig. 122. — .\ll-steel interurban car. St. Louis Car Co. 

been encountered in handling the traffic and maintaining sched- 
ules former h^ handled and maintained by cars weighing two or 
three times as much. The great passenger carrying capacity, 
low energ}^ consumption, and facility for operation on congested 







-■ -- --- 


^ 


1 


h ill "^'-^^^/A^'iii 


M" :: asi 


UW^BB-H-H^%J. 


■ ... 


-^^^BL:..ar^., - :.. :-i:-:- ' . -SH 


1 


u ■ "• ■ 

1— '" • - • -^-^ " 


:. ' K'^^ ^^T, 



Fig. 123. — ^ew York elevated and subway car. 

streets, which these cars possess, have opened a new field for them 
in this class of interurban service. 

Elevated and Subway Cars. — In the elevated and subway ser- 
vice in the largest cities a sUghtly different type of car is required, 
although it is patterned closely after the interurban car. Exits 
are so located as to be flush with the platform floors, no steps be- 
ing necessary. In Boston and Xew York both side and end doors 

1 Pittsburgh Railways, Electric Railway Journal, page 250, Aug. 8, 1914. 



272 ELECTRIC RAILWAY ENGINEERING 

are provided and with the traveling public trained to enter by the 
end door and leave the car by the side door, some time is gained 
at the station. Both transverse and longitudinal seats are 
provided. These cars are designed to operate in trains, each train 
consisting of both motor cars and trailers, all motor cars being 
operated by means of the multiple unit control from the motor- 
man's cab of the forward car. In the New York subway steel 
cars are now being adopted, one of this type being illustrated in 
Fig. 123. 

While the life of passenger cars will vary from 10 to 20 years, 
depending upon the type, severity of service and the attention 
which they receive in the shops, obsolescence has been the reason 
for discarding most of the cars used thus far, i.e., traffic demand 
has required that larger and better cars replace those in operation 
before the latter were actually worn out. 

Freight Cars. — The car body construction of motor cars used 
in handling freight and express is similar to that of the standard 
express car used in steam railway service. Sometimes these car 
bodies are equipped with extra heavy underframing, trucks, and 
motors, and used as locomotives for hauling short trains of stand- 
ard steam road freight cars. 

Storage Battery Cars. — The great improvements made during 
the last few years in storage batteries, bearings, and light me- 
chanical parts, brought about largely by the wonderful develop- 
ment of the modern automobile, have contributed much to the 
success of this type of car for certain classes of service. In 1913 
there were 280 of these cars in use on 45 different roads in the 
United States.^ The number has increased considerably since 
then. Storage battery cars are particularly well adapted to meet 
the service requirements for: 

1. Crosstown lines with light traffic. 

2. Lines where either narrow streets or legal requirements pro- 
hibit overhead construction. 

3. Very small roads. 

4. Accommodation trains on short steam roads and light 
traffic branch line service in connection with large steam railway 
systems. 

In order to minimize the energy consumption great care is 
taken in the design of these cars. Usually all of the bearings 
are of either the ball or roller type, the car ends are shaped to 

1 Electric Railway Journal, Oct. 4, 1913. 



CARS 



273 



minimize air resistance, and all unnecessary weight is eliminated. 
A car recently purchased by the Cambria & Indiana Railroad, a 
short coal road in Pennsylvania, has a seating capacity of 52, is 
50 ft. long and weighs 29.5 tons. It has baggage, smoking and 
toilet compartments in addition to the regular passenger com- 
partment, and is equipped with four 25 hp. motors and 240 
Edison A-12 cells for power and 10 Edison A-12 cells for lighting. 




Fig. 124. — Plan of gas-electric car. 

The battery equipment weighs 7 tons. The car has a maximum 
range of 130 miles on level track and a maximum speed of 35 
m.p.h. 

Gas Electric Car. — In several instances, particularly upon 
branch roads acting as feeders to trunk lines, where traffic is light 
and the installation of an electrical distribution system therefore 
unwarranted, and yet where the advantages of electric traction are 
worthy of serious consideration, the gas electric car has found a 




Fig. 125. — Elevation of gas-electric car. 



place. This car not only provides for from 40 to 50 passengers, 
together with a baggage compartment, but also is a complete 
power plant, a flexible distribution system and a motor car 
combined. In the front end, above the floor, is located an 8 
cylinder, 100/125 hp., 4-cycle gas engine, direct connected to 
an 80 kw., 600 volt commutating pole direct current generator 
with exciter. A series-parallel controller regulates the supply 

18 



274 ELECTRIC RAILWAY ENGINEERING 

of current from this generator to two 100 hp. motors mounted on 
the front trucks. Additional flexibility of control is provided by 
the regulation of the voltage supplied to the motors by the varia- 
tion of the generator field strength. The controller is also pro- 
vided with means for regulating the engine ignition and the 
throttle. The car may be started, stopped and reversed with 
the engine running continuously in one direction. A trolley is 
often provided by means of which the car may be operated on 
standard direct current trolley systems without change in the 
control equipment. 

Reports from roads where these cars have been installed show a 
marked reduction in operating expenses and maintenance charges 
over those of steam operated trains, although their comparatively 
recent introduction has not permitted an accurate comparison 
over an extended period. A plan and elevation of one of these 
cars may be found in Figs. 124 and 125 respectively. 



CHAPTER XXII 
MOTORS 

Much of the theory underlying the operation of 'the direct 
current series motor has been discussed in a previous chapter. 
A brief outline of its construction and selection, together with the 
principle of operation of the alternating current motors used in 
railway systems, will be herein considered. 

Direct Current Motor. — The direct current series railway 
motor differs from the stationary type principally in the design 
of the frame, that of the former motor consisting of an iron 
casting split in a plane through the center of the shaft and 
hinged in such a manner that the lower half of the frame 
with two field poles and windings may be lowered for inspection 
of the armature with the motor in place on the truck. The larger 
motors, Fig. 126, are of the so-called '^box" type with the frame 
in a single casting. The armature is removed from this motor by 
taking off the end bearing plate and drawing the armature out in a 
direction parallel with the shaft through the opening thus made. 
The motor must be removed from the truck for this operation. 
The frames of both types of motors are provided with openings 
and moisture-proof cover plates for ready access to armature, com- 
mutator and connecting cables. These cables are brought out 
through insulating bushings in the frame of the motor, which are 
usually located on the side next to the truck bolster, in order that 
the movement of these cables may be least when rounding curves. 

Railway motors are generally of the four pole type with the 
axes of the poles at an angle of 45 deg. with the horizontal in the 
split frame types. Field coils are wound with cotton or asbestos 
covered wire with asbestos insulation between layers or in the 
larger motors with copper strip. The coils are taped, impreg- 
nated with insulating compound with the vacuum process and 
water-proofed. 

Two sets of bearings are provided in the frame, one pair for the 
car axles and the second for the armature shaft. These are 
of babbitt lined cast bronze. 

275 



276 



ELECTRIC RAILWAY ENGINEERING 



The armature and commutator are not unlike those of station- 
ary motors except that the armature is series wound and requires 
but two sets of brushes. These are placed on the top portion 
of the commutator and are therefore accessible through trap 
doors in the floor of the car. The brush holders are fixed in posi- 
tion and support the carbon brushes in a radial position on the 
commutator so that the motor may operate equally well in either 
direction. 

Commutating Pole Motor. — As in the case of direct current 
stationary motors and generators, the rather marked advantages 
of the commutating pole are applied to the railway motor. These 
commutating poles are auxiliary poles provided with a winding 
connected in series with the armature. As the magnetic flux 




Fig. 126. — Typical box type railway motor. 



in these poles will vary with the armature current, the serious 
effects of armature reaction upon commutation are partially 
neutralized by the flux from these auxiliary poles. The latter 
are so designed and located that the short circuit current in the 
coil under the brush is small and sparking at the brushes therefore 
a minimum. As the output of the motor is often limited by com- 
mutation as well as temperature rise, the overload capacity will 
be increased and its maintenance cost reduced. It is claimed 
that 100 per cent, overload may be suddenly thrown on and off 
such a motor without sparking at the brushes. 

Field Control Motors. — A comparatively recent departure in 
d. c. railway motor design is the construction of the field coils in 
two distinct parts on the core of the pole, the two parts being 



MOTORS 



277 



insulated from each other. The part which is to be in continu- 
ous service has tlie larger number of turns. The smaller coil of a 
less number of turns is used only in accelerating the car. The 
four larger coils of the main operating fields are connected per- 
manently in series and likewise the four smaller coils are similarly 
connected. When the car is being accelerated the eight coils are 
in series, thus producing a more powerful field and a correspond- 
ingly greater tractive effort for the same value of current than if 
the group of four larger coils alone were in the circuit. When the 
car has nearly reached full speed the series of smaller field coils is 
cut out, thus reducing the field and giving higher speed for a given 
current. 

The saving of energy with field control motors may be quite an 
appreciable amount, it being from 6 to 10 per cent, in frequent 
stop city service and from 4 to 7 per cent, on elevated lines. 

Pressed Steel Motors. — Of still more recent development is the 
pressed steel motor, Fig. 127. Open hearth steel plates are 




Fig. 127. — Pressed steel motor. Westinghouse Elect. & Mfg. Co. 

pressed into the desired shapes by enormous presses for the yoke, 
frame and other integral parts of the motor. These are all assem- 
bled and held together by hot-driven rivets. The result is a motor 
whose iron parts are 30 per cent, less in weight in the 30 to 50 hp. 
sizes, and still lighter in proportion in larger ratings, whose mag- 
netic circuits can be operated at a higher density on account of the 
better magnetic qualities of the steel and whose every part is 
strong, unbreakable, free from blowholes and in all ways more 
reliable than the cast steel parts of the ordinary motor. 

The principal drawback to the manufacture of pressed steel 
motors is the expensive equipment required for pressing out the 
motor parts. This factor restricts the manufacture of this type 
of motor to the most popular ratings. 



278 ELECTRIC RAILWAY ENGINEERING 

Single-phase Motors. — With the increase in length of inter- 
urban lines and their large power demands, together with the 
realization of the high first cost and maintenance charges on the 
converting equipment necessary for long direct current roads, 
came the serious study of the possibilities of alternating current 
motors for railway use. It was at once recognized that if a 
satisfactory alternating current railway motor could be developed 
considerable saving could be made in the above factors and a 
marked simplification in the distribution system effected, as 
pointed out in the chapter on the distribution system, to say 
nothing of the possible reduction in distribution system losses 
due to the increase in trolley voltage. As the polyphase motors 
which have been developed were of the constant speed type 
with inherent characteristics unfavorable in most cases for trac- 
tion, and since the advantages of polyphase transmission at high 
voltage can be gained without the complication of a polyphase 
distribution system and car circuits, the attention of American 
engineers was first turned to the development of the single-phase 
motor for traction purposes. 

This development may be approached either by endeavoring 
to adapt the direct current series motor, whose characteristics 
have proved satisfactory for traction purposes, for use upon 
single-phase alternating current circuits, or the alternating current 
induction motor may be studied with a view toward redesigning 
it for railway use. Both of these viewpoints will be considered 
in the order mentioned. 

Adaptation of the Direct Current Series Motor. — Those famil- 
iar with the direct current motor will remember that a reversal 
of the current in either armature or field alone will reverse the 
direction of rotation of the motor, whereas a reversal of both 
field and armature connections will not change its direction of 
rotation. It might be predicted therefore that when a direct 
current series motor is connected to an alternating current circuit 
of proper voltage, the motor would operate. This was found to 
be the case, although many effects of the alternating current, 
which are discussed below, cause the motor to operate unsat- 
isfactorily from a practical standpoint unless several changes 
are made in its design. 

The e.m.f. impressed upon a direct current series motor is 
balanced by the sum of counter e.m.f. of- revolution (Er) and the 
{IR) fall of potential in field and armature windings. In addition 



MOTORS 



279 



to these there exists in the series motor operating upon an alter- 
nating current circuit the reactive voltage of the series field and 
armature windings. 

The reactive voltages are due to the self induction of the re- 
spective windings or better to the cutting of the conductors by 
the lines of leakage magnetic flux which encircle one set of con- 
ductors only and are therefore not useful in producing counter or 
energy electromotive force. This voltage is 90 deg. in advance of 
the current and may be treated as though there were an external 
choke coil of corresponding reactance connected in series with 




E, IR, 

Fig. 128. — Vector diagram for A. C. series motor. 

the motor. It is directly proportional to the frequency of the 
voltage supply. 

With these voltages in mind the vector diagram of the motor 
may be drawn as in Fig. 128 where 

E = Impressed voltage. 

= Counter e.m.f. of revolution. 

= Current in armature and field. 

= Resistance of armature. 

= Reactance of armature. 

= Resistance of field. 
Xf = Reactance of field. 

</) = Angle between impressed voltage and current 
whose cosine is the power factor of the motor. 

From the diagram it will be seen that any change of design 
that will reduce (X/) and (Xa) will increase the power factor of 
the motor. This is a desirable change as a higher power factor 
results in smaller losses and higher torque in the motor not only, 
but either lower losses or less copper in the distribution system 
as well. The reactance voltage of the armature (/Xa) may be 



Er 
I 

Ra 

Rf 



280 



ELECTRIC RAILWAY ENGINEERING 



more or less completely neutralized by means of a compensating 
winding which will be subsequently explained, while that of the 
field can only be reduced by reducing the turns on the field or 
the magnetic flux produced thereby. 

Before these possible changes are studied further the question 
of commutation may well be investigated, for the commutation 
of a direct current motor operating upon alternating current 
is noticeably poor. It will be remembered that in the commuta- 
tion of direct current motors, care must be taken to have the 
current a minimum in the coil or coils which are short circuited 
by the brushes in order that the spark which occurs when the 
coil is disconnected from the brush by the movement of the com- 
mutator may not be serious. Reference to Fig. 129 will show, 
however, that there is an additional factor to be considered in the 




Fig. 129. — Circuit of A. C. series motor. 



commutation of an alternating current motor. The motor is 
quite similar to a transformer in that it has a magnetic circuit 
surrounded by two sets of coils, the field and the armature. The 
pulsating flux set up by the field generates an electromotive force 
due to this transformer action in the coils of the armature, those 
coils in the plane {a'h') which enclose the greatest number of 
magnetic lines of force generating the highest voltage and those 
in the plane {ah) theoretically zero voltage. But one or more of 
the coils in plane {a'h') are short circuited by the brushes. A large 
current fiows through this coil therefore as in the case of a short 
circuited secondary coil on a transformer. Unless the design 
is altered so as to reduce this current, vicious sparking will take 
place and seriously limit the commutating capacity of the motor. 
Two methods of reducing this short circuit current are in 



MOTORS 281 

general use. One makes use of an auxiliary stator coil placed 90 
electrical degrees from the field coils as in the case of the commu- 
tating poles on direct current motors. This so-called ''compen- 
sating" coil is in series with the armature and is designed of such 
strength as to neutralize the combined effect of transformer e.m.f. 
and armature reactance e.m.f. While such a coil can be made 
to perform such neutralization for one load and partially neu- 
tralize the e.m.f. on all loads, its effect is not complete over the 
entire range of load, it being particularly faulty at very light loads. 
One of the large manufacturing companies overcomes this light 
load fault by inserting ''preventive'' leads between the point 
where connection is made between armature coils and the com- 
mutator. These leads are of relative^ high resistance and there- 
fore tend to limit the short circuit current to a minimum. As 
the current circulating through the armature coils encounters 
the resistance of the preventive leads only as it flows into or out 
from a brush, the heat loss in the leads is not large. The com- 
bination of compensating coils and preventive leads not only 
puts the commutation of the alternating current series motor on 
a par with that of the direct current motor, but it increases the 
power factor to a practical operative value as well. 

Returning to the question of reducing the reactance e.m.f. 
of the field in order that the power factor may be still further 
increased. If this be done by reducing the field flux, the capacity 
of the motor is correspondingly lowered. It is actually accom- 
plished in practice, therefore, by reducing the number of field 
turns to from 20 to 25 per cent, of those in a direct current motor 
of similar characteristics. This is rather difficult with the large 
capacity motors having a relatively large number of poles. 

Aside from the above changes in design which are necessary 
in order to adapt the direct current motor to use with alternating 
current, the field must be laminated as well as the armature to 
prevent serious eddy current losses. The reluctance of the 
magnetic circuit must be reduced in order that the flux may not 
be sacrificed with a smaller number of field turns and joints are 
therefore eliminated and the sectional area of the poles increased. 
Theoretically the length of the air gap might be shortened to 
produce the desired reduction in reluctance, but this is not con- 
sidered advisable from a practical operating standpoint, for with 
the direct current motors the bearings often wear to such an ex- 
tent that the armature rubs on the lower field poles. 



282 ELECTRIC RAILWAY ENGINEERING 

Adaptation of Induction Motor. — The evolution of the single- 
phase induction motor into the alternating current series railway 
motor has been very clearly explained from the theoretical stand- 
point by McAllister. 1 Briefly the development is as follows: 
Suppose a single-phase induction motor stator to be provided 
with an armature similar to that of a direct current series motor 
and the stator and armature windings to be connected in series. 
McAllister shows very clearly that with all possible ratios of field 
to armature turns the power factor will not exceed 45 per cent, 
and the maximum limit of the ratio of starting to synchronous 




Fig. 130. — Single phase series motor. 

torque will be in the neighborhood of 125 per cent. Both of these 
values are too small for a satisfactory railway motor. 

If the reluctance of the air gap between polar regions be in- 
creased by forming polar projections in the stator fields or by a 
neutralizing winding such that the ratio of reluctance of the leak- 
age path between poles to that under the poles may be considered 
as infinite, the power factor and torque ratio may be increased 
over a wide range by properly proportioning the armature and 
field turns. The successful railway motor may be considered, 
therefore, as an induction motor stator with high reluctance 

1 "Alternating Current Motor" by A. S. McAllister, 



MOTORS 



283 



between poles, enclosing an armature similar in design to that 
of a direct current series motor. 

Construction of the Single-phase Motor. — As the result of 
the above studies a motor has been developed which is giving 
very satisfactory results upon single-phase railway systems of 
low frequency (25 cycles) especially in the larger sizes which have 
been applied to locomotives. 

Such a motor, Fig. 130, does not appear materially different 































































CHARACTERISTIC CURVES 

OF 125 H.P. SINGLE PHASE 

25 CYCLE A.C. MOTOR 
DIAMETER OF WHEELS 37 V2 
GEAR RATIO 2.33 






Oh' ^ 










Speed 
3r Cent Effici 


















\ 


























\ 
















/ 


Pu 
50 100 

90 










\ 














/ 


/ 












\ 


■— 


£0T 


K 


^act( 


^^- > 


/ 














get 


^Efi 


licjehey 


X 




- 


40 80 

70 

30 60 

50 
20 


' 


\ 


""T^ 








^ 








Ni.. 


/ 
























^* 


>, 




















4 






^ 


b 
















A 


r 








^v 


"-^ 














cf/ 


/ 














10 










y\ 


/ 






















^ 


y 

























^ 


^ 























o 
5?^ 



2400 



2000 



1600 



1300 



800 



400 



100 



200 



300 400 

Amperes 

Fig. 131. 



500 



700 



from the direct current motor, consisting of a cast steel box type 
frame supporting the laminated iron stator. The motors are 
provided with four or six poles and their field windings are of the 
distributed type similar to those of the single-phase induction 
motor. The winding is of heavy strap copper, however, and con- 
sists of a relatively few turns. Between the main field windings 
are located the compensating windings connected in series with 
the armature. The armature is practically identical with that 



284 



ELECTRIC RAILWAY ENGINEERING 



of the direct current motor with the exception that because of the 
lower voltage and consequently higher current for which it is 
designed it is usually necessary to provide one set of brushes for 
each pole. 

Characteristics. — The characteristics of the single-phase motor 
are strikingly similar to those of its competitor, as will be seen 
by comparing Figs. 131 and 132. The efficiency of the former 
motor is slightly lower and the torque-current curve slightly more 
concave owing to the lower induction for which the alternating 




100 125 150 175 200 225 

Amperes 

Fig. 132. — Characteristic curves of Westinghouse D. C. 303 A, 115 hp. 
motor, 600 volts, diam. wheels 33 in., gear ratio 2.21. 

current motor is designed. With the fields unsaturated, therefore, 
the torque will vary with the square of the current. 

Operation on Direct Current. — One of the most important 
features to commend the single-phase series motor as above de- 
scribed is its satisfactory operation on direct current circuits. If 
the changes which have been made to adapt the motor to alter- 
nating current are reviewed it will be noted that no change made 
impairs its use with direct current. Since it is highly important 
that interurban roads operate their cars to the center of the termi- 
nal cities over the existing direct current trolley, this feature of the 



MOTORS 



285 



series alternating current motor is of greatest value. Whereas 
the control system must be duplicated to some extent, as will 
be seen in the next chapter, the flexibility of operation is well 
worthy of the slightly added complication. 

Repulsion Motor. ^ — When it was found that a corrective 
current could be made to flow in the armature of an alternating 
current motor by means of induction between windings as in 
the case of the transformer, it was inferred that such a current 



Pi 70 
^-60 



1^0 
5? 40 



m30 



(220 



10 







\ 












/ 






\ 






' — <^ 




'^ncy 


/ 


400 










\ 






*-<<^ 


^w 


^ 














/ 


^ 


^ 


800 








\ 


,ot^ 


/^ 






200 






















# 


> 


\i 




[^ 




lOO 




/ 


Cl 


d/ 


V 


\- 




"^ 






v^ 






-% 


fe-^o 


















<; 


-\ 



4500 



16000 



3500 % 
o 
> 812000 

\ 3 

\ 2500 . 



,^ 1500 



500 



8000' 



4000 



500 



1000 
Amperes 



1500 



2000 



Fig. 133. — Characteristic curves of 250 hp., single phase, 25 cycle, A. C. 
motor, 235 volts, diam. wheels 63 in., gearless. 



might be made to produce a torque without connection between 
armature and field as in Fig. 134. Such a motor was found to 
operate satisfactorily, the brushes being short circuited to allow 
the torque producing currents to flow in the armature windings. 
The characteristics of such a motor are similar to those of the 
series motor. This motor has been designated as the repulsion 
motor. Although it was expected that it would find a ready ap- 
plication in the railway field it has not come into use largely 
because of its inability to operate upon direct current systems 

i"The Alternating Current Railway Motor, " by C. P. Steinmetz, A. I. E. 
E., Vol. XXIII. 

''Speed Torque Characteristics of the Single-phase Repulsion Motor," by 
Walter I. Slichter, A. 1. E. E., Vol. XXllI. 

"Alternating Current Motors," by A. S. McAllister. 



286 



ELECTRIC RAILWAY ENGINEERING 



Series Field 



and the additional fact that it apparently has no marked ad- 
vantages over the series motor. 

Induction Motor. — It will be remembered that the alternating 
current induction motor, as its name implies, has no electrical 
connection between stator and rotor. It is therefore a much 
simpler motor than others used for railway service which involve 
the use of, commutators and its maintenance expense is therefore 
correspondingly less. The induction motor has the disadvantage, 

however, of constant speed 
characteristics similar to those 
of the direct current shunt 
motor which has never proved 
satisfactory for railway ser- 
vice. 

This disadvantage of nearly 
constant speed at all loads 
may be partially overcome, 
however, by making use of 
one or more of three prin- 
ciples : 

A winding may be placed 
upon the rotor instead of the 
usual short circuited " squirrel 
cage" construction and the 
taps from this winding 
brought Out to slip rings. 
This permits varying resis- 
tances to be inserted into the 




Compensating 
Field 



Fig. 134. — Circuit of repulsion motor. 



rotor circuit which in turn produces varying speeds at the ex- 
pense of lowered efficiency. 

Secondly, the so-called ^'concatenation" method may be 
adopted in which the stator of the second motor is connected to 
the rotor of the first through the agency of slip rings and the 
rotor of the second motor is provided with variable resistances 
as in the first case. Thus a low frequency is impressed upon the 
stator of the second motor depending upon the speed of the rotor 
of motor number one and a wider range of speeds produced 
thereby with less energy lost in heating of resistances. 

A third but less used method involves the changing of stator 
connections in such a manner as to create varying numbers of 
poles in the stator. Since the speed for a given frequency of 



MOTORS 



287 



supply is dependent upon the number of poles, a series of speeds 
may be made available in this manner with little sacrifice of 
efficiency. The complication of control circuits when this 
method is used makes it prohibitive if many different speeds are 
required. 

Although a rather extensive use of the induction motor has 
been made abroad for many years, its installation in this country 
has been confined to two sections of electrified trunk lines, i.e., 
the Cascade Tunnel of the Great Northern Railway and a moun- 
tain grade division of the Norfolk & Western Railroad in Virginia. 
In the former system, although the variation of the number of 
stator poles was at first considered, it was finally abandoned in 




Fig. 135. — Rotor of Norfolk & Western induction motor. 



favor of the first method of control outlined above. This was 
further simplified by varying the iron grid resistances in the va- 
rious phases of the rotor consecutively instead of keeping the 
currents balanced. This departure from stationary motor prac- 
tice provided several speed changes with a minimum of control 
connections but was accompanied, of course, by unbalanced cur- 
rents in the motors. The Norfolk & Western Railroad, on the 
other hand, makes use of a rather unique combination of single- 
phase distribution for three-phase motors through the agency of a 
phase converter mounted upon the locomotive. The rotor 
of this motor is illustrated in Fig. 135. In both of these instances 
the grades are heavy, the speeds low and the number of required 



288 ELECTRIC RAILWAY ENGINEERING 

stops very small. For such service only is the induction motor 
considered advisable at present in spite of its advantages of sim- 
plicity, low maintenance charges and its ability to regenerate 
energy upon down grades. 

Frequency. — The question of frequency has not been directly 
referred to in the above discussion. If reference be made again 
to the factors which were necessarily changed in the direct current 
motor to adapt it to alternating current operation it will be noted 
that these factors, principally reactance voltages, are reduced by 
reduced frequency. The lower the frequency, therefore, the 
easier it becomes to design a satisfactory alternating current rail- 
way motor and the greater the capacity which it is possible to 
obtain with a given size and weight of frame and, therefore, the 
greater the capacity that can be supplied to a single truck or to a 
single pair of driving wheels. 

Motor Design. — Although the details of motor design cannot 
be discussed at length, a few of the mechanical features which 
must be given careful consideration by the designer and the rail- 
way operator may well be called to mind. Most of the difficult 
problems in connection with the design and construction of rail- 
way motors result from the necessity of crowding a large amount 
of power into a space necessarily limited by standard wheel gauge, 
demands for light weights, low car floors and large clearances be- 
tween motor frame and track. Large gear ratios are usually 
desirable, especially in city service, in order to keep the energy 
consumption low and to make use of a high speed and therefore a 
light and inexpensive motor. Large gear ratios, however, neces- 
sitate smaller clearances, thinner bearing sleeves, smaller axles and 
low pitch gears, any one of which results may prove objection- 
able if not carefully limited. The designer, and the representative 
of the operating company responsible for motor specifications 
must, therefore, adopt a compromise between these extremes. 

The selection of bearing metal is also a compromise. A bab- 
bitted bearing in a steel shell is cheapest, most easily repaired 
and offers a superior wearing surface for high speeds. On the 
other hand, it is impossible to obtain the intimate amalgam bond 
between babbitt and steel that exists between babbitt and brass 
or bronze and the lining is likely to work loose. Further, if there 
is any play in the box its seat in the frame is apt to be seriously 
worn if a steel shell is used. Babbitt also wears rapidly and the 
thickness necessary to line a steel shell may wear sufficiently to 



MOTORS 289 

cause the armature to drop and rub upon the lower field poles. 
To overcome these difficulties a bronze shell with a very thin inner 
sleeve of babbitt or merely a tinned surface has come into rather 
general favor. 

The problem of suitable lubrication has also proved a vexing 
one for many years. Grease was generally used at first as a 
lubricant through the agency of separate grease cups first tapped 
into the bearing shell and later cast integrally with the motor 
frame. Recently the use of oil in a journal packed with waste 
similar to that in the truck journal has been used very extensively, 
the capillary action of the oil in the waste being depended upon 
to supply lubricant to the axle. 

In the attempt to provide more power in a given space the ven- 
tilation of the motor has been studied to advantage recently. 
Forced ventilation has occasionally been resorted to, but this adds 
expense and complication to the equipment. Early attempts to 
provide ducts of large cross section in the motor through which 
air might be forced by the motion of the car resulted in collecting 
too much dirt and moisture for the successful operation of the 
motor. Recently, however, ventilated motors have been fur- 
nished with an air intake at right angles with the direction of 
motion of the car which prevents this difficult}^ The air enters 
at the upper and pinion end of the motor and passes between 
the field coils, over the surface of the armature, under the commu- 
tator, back parallel with the shaft through holes in the armature 
laminations and is then forced into the atmosphere by means 
of a radial fan. Such ventilation has been claimed to have in- 
creased the possible load per motor for a given temperature rise 
by 39 per cent, with a relatively large number of stops and 42 per 
cent, in service with few stops. 

Whereas numerous types of suspensions were designed and used 
with early motors for supporting the motor upon the truck, 
the ''bar" and ''nose" suspensions are now almost universal. 
It is obviously necessary to provide car axle bearings in the frame 
of the motor and so to suspend the other side of the motor from 
the truck that it may swing about the car axle as a center when 
passing over irregularities in the track in order that the gears 
may always be kept in mesh. The two suspensions mentioned 
above differ only in the manner of supporting this free side of the 
motor frame. The "bar" suspension has a bar or yoke bolted 
to the frame of the motor which is spring supported from the truck, 

19 



290 ELECTRIC RAILWAY ENGINEERING 

while in the ''nose" suspension a single ''nose" or lug is cast 
upon the motor frame which is supported from the truck by means 
of a link. In both cases it is now considered desirable to have 
additional lugs cast upon the motor frame to catch the motor and 
prevent it from falling to the track in case of the failure of the 
normal suspension. 

Rating. — Railway motors, because of their rather intermittent 
service at varying loads with a greater amount of ventilation in 
actual use than upon the testing floor, are rated differently than 
other electrical machinery. 

A great advance has been made recently by the Standardiza- 
tion Committee of the A. I. E. E. in establishing ratings for rail- 
way motors. 

The "nominal" rating is defined by this committee as "the 
mechanical output at the car or locomotive axle, measured in 
kilowatts, which causes a rise in temperature not exceeding 90°C. 
at the commutator, and 75°C. at any other normally accessible 
part after 1 hour's continuous run at its rated voltage (and 
frequency in the case of an alternating current motor) on a stand 
with the motor covers arranged to secure maximum ventilation 
without external blower. The rise in temperature as measured 
by resistance shall not exceed 100°C. 

The "continuous ratings" of a railway motor are defined as 
"the inputs in amperes at which it may be operated continuously 
at 3^^, % and full voltage respectively without exceeding the speci- 
fied temperature rise (Table XXXII) when operated on stand 
test with motor covers and cooling system, if any, arranged as in 
service." 

Since in railway service the loads upon the motors are varying 
over wide ranges, the "maximum input rating" of the motor be- 
comes of interest. The committee states in this connection that 
"railway motors shall be capable of carrying twice the current 
corresponding to their nominal rating for a period of 5 minutes, 
without flash over or mechanical injury. They shall also be 
capable of carrying a load of three times their nominal rating 
for 1 minute under the same conditions. These overloads shall 
be applied when the motor is at the temperature which it would 
acquire when operating at its continuous rating." 

Although the temperatures which are permitted in railway 
motors are based upon the kind of insulating materials used, as 
previously explained for power station and substation machinery, 



MOTORS 



291 



the conditions under which the railway motor is operated with 
respect to ventilation, limited space and weights, etc., have led 
to a higher allowable temperature for short periods of time than 
was permitted for other classes of electrical machinery. Table 
XXXII indicates permissible maximum temperatures and tem- 
perature rises for railway motors. 

Table XXXU. — Permissible Temperature Rise in Railway Motors 



Insulation 


Maximum 1 
Short period 


temperature 

Continuous 


Temperature rise 
on stand test 




Ther. 


Resist. 


Ther. } Resist. 

1 


Ther. 


Resist. 


Treated cotton, silk, 


100 


125 


85 


110 


65 


85 


paper and fibrous 














material, including 














enamel wire. 














Mica, asbestos and other 


115 


145 


100 


130 


80 


105 


high temperature resist- 














ing material. 















It should be noted that whereas motors were formerly rated in 
horse power, they are now rated in kilowatts. In order to avoid 
confusion during the period in which the new method is being 
adopted, the A. I. E. E. recommends that both old and new rat- 
ings be given by manufacturers. 

Motor Selection. — The method of determining the total power 
required to operate the car has been explained in a previous 
chapter. After the number of motors per car has been decided 
upon as outlined in the last chapter, the capacity of the motors 
to be installed may be approximately determined by dividing the 
average car demand expressed in horse power for the various 
runs by the number of motors per car. If care be taken not to 
load the motor continuously with its rated load and still make 
due allowance for its overload capacity for short intervals and 
the extra demands of abnormal service, this method should per- 
mit a correct selection of the nearest standard motor to be 
made. 

In most cases a selection of the proper motor must be based 
principally upon test data, and the apphcation of results obtained 
upon the test floor to service conditions is often a difficult prob- 
lem. The recommendations found in the standardization rules of 



292 ELECTRIC RAILWAY ENGINEERING 

the A. I. E. E. bearing upon this subject are therefore quoted in 
considerable detail. 

"In comparing projected motors and in case it is not possible or 
desirable to make tests to determine mechanical losses, the following 
values of these losses, determined from accumulated experience, will be 
found useful. They include axle bearing losses, gear losses, armature 
bearing losses, brush friction losses and windage. 



Per cent, of nominal rating 


Losses as per cent, of input 


150 


5.0 


125 


5.0 


100 


5.0 


75 


5.0 


60 


5.3 


50 


6.5 


40 


8.8 


30 


13.3 


25 


17.0 



''The core loss of railway motors is sometimes determined by sepa- 
rately exciting the field and driving the armature of the motor to be 
tested by a separate motor having known losses and noting the differ- 
ences in losses between driving the motor light at various speeds and 
driving it with various field excitations. 

''The core losses at other loads shall be assumed as follows: 

At full continuous rated input 1.2 times no load core loss. 

At half continuous rated input 1.1 times no load core loss. 

"The multiplier for other loads shall be in the same proportion. 

"Selection of Motor for Specified Service. — The following informa- 
tion relative to the service to be performed is* required in order that 
an appropriate motor may be selected. 

(a) Weight of total number of cars in train (in tons of 2000 lb.) 
exclusive of electrical equipment and load. 

(5) Average weight of load and durations of same, and maximum 
weight of load and durations of same. 

(c) Number of motor cars or locomotives in train, and number of trail 
cars in train. 

(d) Diameter of driving wheels. 

(e) Weight on driving wheels, exclusive of electrical equipment. 
(/) Number of motors per motor car. 

(g) Voltage at train with power on the motors — average, maximum 
and minimum. 

(h) Rate of acceleration in m.p.h. per second. 



MOTORS 293 

(i) Rate of braking (retardation in m.p.h. per second). 

(j) Speed limitations, if any (including slowdowns). 

(k) Distances between stations. 

(l) Duration of station stops. 

(m) Schedule speed, including station stops in m.p.h. 

(n) Train resistance in pounds per ton of 2000 lb. at stated speeds. 

(o) Moment of inertia of revolving parts, exclusive of electrical 
equipment. 

(p) Profile and alignment of track. 

(q) Distance coasted as a per cent, of the distance between station 
stops. 

(r) Time of layover at end of run, if any. 

"Stand Test Method of Comparing Motor Capacity with Service 
Requirements. — When it is not convenient to test motors under actual 
specific service conditions, recourse may be had to the following method 
of determining temperature rise. 

The essential motor losses affecting temperatures in service are those 
in the motor windings, core and commutator. The mean service condi- 
tions may be expressed as a close approximation, in terms of that con- 
tinuous current and core loss which will produce the same losses and 
distribution of losses as the average in service. 

A stand test with the current and voltage which will give losses 
equal to those in service will determine whether the motor has sufficient 
capacity to meet the ser^dce requirements. In service, the temperature 
of an enclosed motor well exposed to the draught of air incident to a 
moving car or locomotive will be from 75 to 90 per cent, (depending 
upon the character of the service) of the temperature rise obtained on a 
stand test wdth the motor completely enclosed and with the same losses. 
With a ventilated motor the temperature rise in service will be 90 to 
100 per cent, of the temperature rise obtained on a stand test with the 
same losses. 

In making a stand test to determine the temperature rise in a specific 
service, it is essential in the case of a self ventilated motor to run the 
armature at a speed w^hich corresponds to the schedule speed in service. 
In order to obtain this speed it may be necessary, while maintaining 
the same total armature losses, to change somewhat the ratio between 
the PR and core loss components. 

"Calculation for Comparing Motor Capacity with Service Require- 
ments.' — 'The heating of a motor should be determined, wherever 
possible, by testing it in service or with an equivalent duty cycle. 
When the service or equivalent duty cycle tests are not practicable, the 
ratings of the motor may be utilized, as follows to determine its tem- 
perature rise. 

The motor losses which affect the heating of the windings are as stated 
above, those in the windings and in the core. The former are propor- 



294 ELECTRIC RAILWAY ENGINEERING 

tional to the square of the current. The latter vary with the voltage 
and current, according to curves which can be supplied by the manufac- 
turers. The procedure is therefore as follows : 

(a) Plot a time current curve and a time voltage curve for the duty 
cycle which the motor is to perform, and calculate from these the root- 
mean-square current and the equivalent voltage which with r.m.s. 
current will produce the average core loss. 

(6) If the calculated r.m.s. service current exceeds the continuous 
rating, when run with average service core loss and speed, the motor is 
not sufficiently powerful for the duty cycle contemplated. 

(c) If the calculated r.m.s. service current does not exceed the continu- 
ous rating, when run with average service core loss and speed, the motor 
is ordinarily suitable for the service. In some cases, however, it may not 
have sufficient thermal capacity to avoid excessive temperature rises 
during the periods of heavy load. In such cases a further calculation is 
required, the first step of which is to calculate the temperature rise due 
to the r.m.s. service current and equivalent voltage. 



Let t = temperature rise 

Po 



Then 



^„D 1 1 With r.m.s. service current and equiva- 

= I^R loss, kw. 1 . • 1. 

1 1 lent service voltage. 

Pc = core loss, kw. j 

T = temperature rise j With continuous load current corre- 

Po = PR loss, kw. I sponding to the equivalent service 

Pc = core loss, kw. J voltage. 

t = T " p approximately. 



(d) The thermal capacity of a motor is approximately measured by a 
coefficient equal' to the ratio of the electrical loss in kw. at its nominal 
(1 hour) capacity to the corresponding maximum observable tempera- 
ture rise. 

(e) Consider any period of peak load and determine the electrical 
losses in kilowatt hours during that period from the electrical efficiency 
curve. Find the excess of the above losses over the losses with r.m.s. 
service current and equivalent voltage. The excess loss divided by the 
coefficient of thermal capacity will equal the extra temperature rise due 
to the peak load. This temperature rise added to that due to the r.m.s. 
service current and equivalent voltage gives the total temperature 
rise. If the total temperature rise in any such period exceeds the safe 
limit, the motor is not sufficiently powerful fo the service. 

(/) If the temperature reached due to the peak loads does not exceed 
the safe limit, the motor may yet be unsuitable for the service, as the 
peak loads may cause excessive sparking and dangerous mechanical 
stresses. It is, therefore, necessary to compare the peak loads with 



MOTORS 295 

the short period overload capacity. If the peaks are also within the 
capacity of the motor, it may be considered suitable for the given duty 
cycle." 

Several other methods of making this selection may be adopted, 
however, and it is always well to check the motor capacity chosen 
by two or more processes. They will be briefly explained in order 
of their ease of application. 

Selection by Comparison. — A very rough and simple method 
quite commonly used is to prepare a table from technical jour- 
nals or the railway census of the equipments of various roads 
operating under as nearly as possible the same conditions as the 
proposed road. This table should include number and capacity 
of motors, average voltage, schedule speed, weight of cars, lay- 
over at terminals, stops per mile, average grade, and if possible 
the watt hours per ton mile demanded. By comparison with such 
a table the correct standard size of motor for the new equipment 
may readily be determined. 

Effective Current Method. — It is possible to obtain from 
manufacturers' test records not only the rating of the motor, but 
also its continuous current capacity at one or more average vol- 
tages, i.e., the current which may be supplied to the motor con- 
tinuously without exceeding the limit of 75°C. temperature rise. 
The temperature curves of Fig. 13 may also be obtained from 
which the time required to rise to 75°C. above the room tem- 
perature from the start with the motor cold can be found for each 
value of current supplied to the motor, as well as the time required 
to rise 20° above 75°C. for the various possible overload currents. 
In making use of these data it should be remembered that the 
heating of a motor is proportional to the square of the current. 
The heating value of the current or '^effective" current for a 
given run is not the average ordinate of the current time curve 
of that run, but the square root of the average squared current. 
If then the effective current for the various runs as determined 
from the current time curves be compared with the continuous 
current rating of the motors with due allowance for temperature 
rise of short duration produced by overload currents as deter- 
mined from the temperature curve, the proper motor may be 
readily selected. In short, a temperature time curve is really 
determined for the various runs and the motor so selected that 
this curve will not exceed 75°C. rise for other than short inter- 
vals of time. 



296 



ELECTRIC RAILWAY ENGINEERING 



Method Proposed by Armstrong. — In a paper before the 
American Institute of Electrical Engineers^ Armstrong suggests 
that a series of curves such as Fig. 136, each representing the 
motor capacity required for a given weight of car per motor and 
for a certain speed, acceleration, etc., be prepared from theoretical 
and practical test data and used for quick approximations of 



40 



,30 

I 

1.30 

02 

CI 

o 
H 



IC 



30 40 60 80 100 120 140 160 180 300 
Commercial Rating of Motor iu H.P . 

Fig. 136. 

motor capacity. Fig. 136 is plotted for straight level track with 
the following assumed values: 

Gross accelerating force, 120 lb. per ton. 

Braking retarding force, 120 lb. per ton. 

Duration of stops, 15 sec. 

Duration of coasting, 10 sec. 
Since these data do not take into consideration grades and 
curvature or other values of acceleration, deceleration, etc., than 
those listed, either a large number of such charts must be plotted 
or the results taken from same carefully corrected for any varia- 
tion of actual from assumed conditions. 

Method Proposed by Storer.^ — This method assumes that a 
certain motor has been tentatively selected and that it is de- 
sired to determine from test under conditions similar to those of 

^ High Speed Electric Railway Problems by A. H. Armstrong, A. I. E. E., 
Vol. XXII. 

2 By N. W. Storer, Street Railway Journal, 1901. 





















/ 


1 




SERVICE CAPACITY CURVES 


/ 




















/ 




















/ 




















.^ 


/ 


















4> 


y 






/' 


/^ 










/ 


/ 




<i,_^ 


^ 


y 










/ 


/ 




^ 






^ 


^ 






/ 


/ 


^ 








h^ 


— 


^ 






/^ 




:r^ 






i'^"^ 











MOTORS 297 

actual service whether or not this particular motor will fulfill the 
requirements. 

The effective current for the various runs is determined as 
explained above and the average voltage at the terminals of the 
motor found from the voltage time curve. If, now, the motor 
be operated with this effective current and with the average 
voltage impressed upon it, the motor losses will be the same as in 
practice and the heating of the motor under service conditions 
may be determined therefrom. It should be remembered, how- 
ever, that the ventilation of the motor is better in service and it 
may usually be depended upon to carry from 20 to 25 per cent, 
more load with the same temperature rise when on the car. This 
allows a good factor of safety if the motor be selected from test 
results. 

Method Proposed by Hutchinson. ^ — The method employed by 
Hutchinson, where a large number of motor determinations are 
to be made by a manufacturing or an engineering company, is 
one involving mathematical equations based upon a large number 
of general charts deduced from the typical speed time curves. 
In place of assuming the straight line speed time curve of Chap. 
X to be correct, a mathematical correction applying to the differ- 
ence in area between the accurate and the straight line speed 
time curve is used and constants derived which, when substituted 
in the equations given, enable the latter to be solved for correct 
motor capacity. For further details reference should be made 
to the original paper. 

Regeneration of Energy. — The ability of the induction motor 
to regenerate energy has been previously referred to. The ad- 
vantages of such regeneration, which is made possible by coast- 
ing down long grades at motor speeds above synchronism, are 
four-fold : 

Less wear in braking equipment and especially in brake shoes. 

Furnishes power to other trains upon the system. 

Reduction of power demand on power station with resulting 
increase in load factor. 

Increased life of rolling stock, couplings and roadbed because 
of snioother descent of grades by heavy trains. 

Whereas these possibilities of regeneration have until recently 
received little consideration, the fact that upon one three-phase 
system abroad the train going down grade was able to generate 

1 A. 1. E. E, Vol. XXI. 



298 ELECTRIC RAILWAY ENGINEERING 

54 per cent, of the energy required by the same train in cHmbing 
the grade has led to the study of further possibihties of this re- 
generation of energy in trunk Hne electrification. This has been 
provided for upon the Norfolk & Western Railroad and the Great 
Northern Railway, the only two systems in this country employ- 
ing induction motors. In the latter case the energy regenerated 
is of secondary importance because of the large amount available 
from the water power of the mountains, and it is therefore dis- 
sipated as heat in rheostats. In spite of this fact, however, the 
advantages of this system of down grade control of trains are 
considered sufficient to warrant its installation. This is further 
proved by tests of actual installations in which 14 per cent, of 
the total energy required by the system was produced by re- 
generation from down grade trains, while less than one-third 
the previous brake shoe wear was experienced when regenerative 
braking was used. 

Although the direct current system does not lend itself to 
regenerative control as readily as the induction motor, the 
proposed 3000 volt direct current installation on the Chicago, 
Milwaukee & St. Paul Railroad is expected to make use of this 
principle. 



CHAPTER XXIII 
CONTROL SYSTEMS 

The necessity of starting a car by first impressing a low 
voltage upon its motors and then gradually increasing the voltage 
as the motors speed up until they are receiving their rated 
voltage, has been previously explained. The advisability of 
maintaining a constant current through each motor during 
the constant acceleration period was also pointed out. Means 
must be provided for regulating the speed of a car and for re- 
versing its direction of motion. It is now necessary to consider 
the various standard control systems which have been devised 
to accomplish the above results. 

T5rpes of Control. — As regards the method of manipulation 
of the motor connections and resistances, control systems may 
be classified either as ''hand operated" or ''automatic." With 
the hand operated type the controller handle is moved notch by 
notch at the discretion of the motorman, while in the automatic 
type a current limiting relay, set for a definite, predetermined 
value of current, fixes the maximum rate of "notching up." 
The motorman may move the controller handle to the "full 
on" position but the relay will permit the "notching up" process 
to go on only at such a rate as will keep the motor current ap- 
proximately constant. Thus, while the motorman may notch 
up his controller as slowly as he wishes, the current limiting relay 
fixes the maximum rate of "notching up." 

The following advantages are claimed for the automatic type 
of control: 

1. Prevents abuse of the motors during the accelerating period. 

2. The rate of acceleration is uniform. 

3. Allows the motorman to devote his attention to signals and 
to the track ahead. 

The disadvantages are: 

1. High first cost and maintenance charges. 

2. Complicated. 

3. It is difficult to set the limit relay so that the car will be 

299 



300 



ELECTRIC RAILWAY ENGINEERING 



1 

Si 

■Ml 


s 

2* 


1 




if 

ll 

C 1=1 








a 

to 

6 


1 
o ^ 








> 

£"'0 
sa 

§ 




II 


^1 
H 

> 

m 


'3 
c 

dj 

1 

e 

CI 

O 


l! 




tH 

o 

a 


o 




a 
o 


o "1 

a £ 








11 

02 >> 




2 ^ 
•3 a 










i-^ 


' 


^ 


' 








— \ ■_] a 






^1= 


M 

c 






a" 


>-i 

^d 

C! 
o 




^ i 


a a 




T 




a a 


a 


c S 


I 




-£3 


:3 
-d 


:3 
-d 






? £3 


o o 
-d -d 






-d 




1 • 1 

-d -d 


"d 


> 
" 
+= a 


3 
















<U 0} 




a) 




oj a> 


aj 


'3 c3 


1 




73 


Cl 






a; fl 


'Si 'So 




•a 




.9 .2 


.2 


1- 


m 






tD 


& 






CO 


u u 








t4 (-< 


^ 


C +J 


bfi 


cl 
o 
o 

.2 

1 


'3 


;d 
o 

4J 






"3^ 


I I 




Cl 




a) a; 
Cl C 


aj 


Cl '% 


M 
•43 


o 


'3 

1 -^ i 




Cl 

.S 


c3 


> -d 

O 3 
03 


0) aj 

al 1 




aj 
to 

s 

'0 




« 

•3 '3 




a; 

•3 


'3 


"Hi. 

a.& s 

3 3"^ 
• TJ a; G 




j3 


"£ 


§ 


111 




^ 


S3 


II 


§30 "o 

a -^ ^ -t3 




-3 




1 is 


1 


-2 "^ J 2 






O 


-s 






-£5 
o 


S §.H § 

-- ^ 


J 


1 


J 


1| §1 
-^ -^ 


1 


^ i'S a 

-a ;^ ^ 


1 cc 


















w 














u m 


P^ 


W 




ij 




« 




Eh 






1^ 




ff ►^ 


« 


w 


s^ 




.^ 
















w 




<i <^ 


<J 


PM 


O 03 

0-3 






















~^'" 




~"^'~ 






















I 






^ 


y 






tuO 
.S 


s 

3 






a 








a 


hi 








(3 


-d "c3 

3 a 
% 





















s 


03 3 






c3 


3 






03 








-d 
-d 








-d 

-d 


W <1 


' 




K 


-< 












•"" 






o 


<u 






(U 








aj 


















1 

o 

-d 
S 






s 

o 

03 








03 

1 
O 

-d 

03 




a 
a 




i 

s 

a 


"0 

H 


d 

s 


"S -d 














































































' 


CI £ 


o 


-d o 




d 








tj 


6 








d 






S .^ 




a . 




























ti| o 


<j 


C3 Q 




Q 








<j 


Q 








< 






M ■ 
































_C 
































'>> M 
















_o 










.2 






& $, 








2 








"=3 t: 


"cS 








^ u 








o 

Cj 














1 


13 

o3 








u £ 

II 






o 






1 








03 O 
?5 


J 
1 










' 























— 




















^ 
































o ^ 


















"o 






>> 








o 


















t. t^ 






u 








-t^ t1 


















*' 






c3 


























^ c 














1 o 


















t u 






























a 














;^ -0 























CONTROL SYSTEMS 301 

accelerated at the proper rate for all conditions of track and 
car loading. 

In order to prevent the current through the motors from 
being increased too rapidly with a hand operated controller the 
following method may be used. A mechanical device is attached 
to the top of the controller which by means of a ratchet and 
pawl prevents the forward movement of the controller handle in 
a single swing, but requires a slight backward movement at 
each notch to disengage the pawl and thereby allow sufficient 
time for the current to decrease to its normal accelerating 
value. 

A classification of control systems, based primarily on type 
of construction, is given in Table XXXIII. 

Main Circuit Control. — In this type of control, a drum con- 
troller to which is connected the various motor and line circuits 
is located on the car platform. For double end operation, two 
controllers connected in parallel, one on each end platform, are 
required. Main circuit controllers are used on practically all 
small cars and on some of the older interurban cars. 

A few of the more important requirements in the construction 
of this type of controller are as follows: 

1. Finger tips must be of such design that they will not 
"stub." 

2. Ample arc chutes must be provided so as to prevent arcing 
between the various live parts and between the live parts and 
the case. 

3. Correctly designed magnetic blowouts must be provided. 

4. Switches must be provided so that a disabled motor or 
pair of motors may be cut out without affecting the operation of 
the remainder of the equipment. 

5. Mechanical interlocks must be provided, so that, (1) the 
motors cannot be reversed when the controller handle is in an 
''on" position, (2) the main drum cannot be turned when the 
reverse handle is in the ''off" position, (3) the main drum can- 
not be turned to the parallel position when one of the motor 
cut-out switches is thrown. 

6. The method of attaching the cables to the contact fingers 
or terminal board must give good electrical contact and yet 
permit changes to be quickly and easily made. 

Rheostatic Control. — The earliest type of control, which 
is now practically obsolete, made use of a rheostat in series with 



302 



ELECTRIC RAILWAY ENGINEERING 



the motors, but did not change the motor connections from start 
to full speed. Two complete revolutions of the controller 
handle were necessary to cut out all the resistance, but the 
rheostat was so designed that the controller handle could be left 
in any position indefinitely and correspondingly small variations 
of speed obtained. 

Series -parallel Control. — Practically all the control systems 
in use with direct current railway motors at the present time, 




MSmmk 



Fig. 137. — K-12 wiring diagram. 

although differing widely in detail, operate upon the series- 
parallel principle. The two motors of a two motor equipment or 
those of each group of a four motor equipment are first connected 
in series with one another and also in series with a resistance. 
This resistance is then reduced by three or four steps until the 
two motors are alone in series across the circuit from trolley to 



CONTROL SYSTEMS 



303 



ground. This notch of the controller is termed a "running'^ 
notch as the controller may be left in this position continuously, 
resulting in about half speed. With the next step, the motors 
are changed from series to parallel connection and a resistance 
again introduced. This resistance is reduced in the succeeding 
steps until upon the last notch all motors are in parallel without 
resistance. This is ordinarily the full speed position, although 



PoIqU 

s 



J 

1 

2 
3 

4 


! 

51 



Motors p Motors 

S 4 

ATJtmnj>k:g::;>4MT ktX^^ 



n R R Motor Motor 

3 1 

T-^^KfijmjirLrb-E^:X^-C:X3-° 

/ T-r;HAnjvimirfn3— C^^ 
|b TJ";nARjmjirwSL::J^-En:}^ 
' c Tr;HJWinriiiH:tC:)}5 -O^ 

CONNECTIONS FOR SMALL CONTEOLLERS 
(CI) 

Fig, 138. — Diagram of controller connections in various notches 






CONNECTXONS FOE LARGi; COIifTEOLLEES 
(b) 



in some types of this control an additional step is employed 
which either shunts the motor field with a resistance or cuts out 
part of the motor field coils. In locomotive series-parallel 
controllers four running notches are sometimes provided: 

1. All motors in series. 

2. Motors in series-parallel. 

3. All motors in parallel. 

4. Motor fields weakened as above described. 



304 



ELECTRIC RAILWAY ENGINEERING 



A K-12 controller, which is commonly found on city cars with 
four motor equipments is shown diagrammatically with motor 
and resistance connections in Fig. 137. The connections for 
the various notches may be readily traced if the heavy black 
horizontal bands representing the copper sectors on the control 
cylinder be assumed to move one numbered notch to the left for 
each change of connections. Care should be taken to trace out 
the reversal of armature connections as the reverse cylinder 
represented by the heavy bands at the right of the figure is turned. 
The switches numbered (19) and (15) are used in cutting out 




Fig. 139.— K-35-D controller. 



one set of motors in case of their failure. The resistance steps 
are so proportioned that if the controller is steadily ''notched up' ' 
an approximately constant current will be maintained through 
each motor. A diagrammatic illustration of the various steps 
is found in Fig. 138. 

Fig. 138, a, is also applicable to two motor equipments provided 
the pairs of motors there shown are replaced by single motors. 
The ''bridge" transition shown in Fig. 138, 6, is used in large 
controllers. Its advantage is that the tractive effort during the 
transition period is more uniform. 



CONTROL SYSTEMS 



305 



As may have been inferred from the above discussion, the 
control resistances are designed to remain in the circuit for a short 
time only and will therefore overheat if they be left in circuit 
continuously. 

The mechanical construction of the series-parallel drum con- 
troller may be noted from Fig. 139, which shows the interior of a 
General Electric K-35-D controller with asbestos barrier opened. 
The main drum with its copper sectors insulated from the shaft 
and engaging copper contact fingers will be seen in the center and 
the reverse drum of similar design on the right. On the left at 
the base of the fingers will be seen the individual blowout 



Fuse and Switch 



To Lights and Pump 
MXr Tripping Switch 
Main Switch- 

It; 




Fig. 140. — Wiring diagram for contactor equipment. 



coils. A sufficient flux is produced by these coils to blow out the 
arc formed between fingers and sectors as the circuits are 
opened. In the upper right corner will be found the motor cut- 
out switches. 

In order to prevent the heavy arcing which occurs inside the 
controller case in large drum controllers, an auxiliary contactor 
equipment is sometimes employed. Instead of the main circuit 
being opened by the drum fingers in the main controller, it is 
opened by two powerful electro-magnetic switches, or contactors 
connected in series, which are placed in a separate box under the 
car. These contactors are actuated by auxiliary contacts on the 
main drum which close or open the operating circuit of the con- 

20 



306 



ELECTRIC RAILWAY ENGINEERING 



tactors as the controller handle is turned to the "on" and "off'' 
positions, respectively. Fig. 140 shows the wiring diagram for 
the contactor equipment as built by the General Electric Company. 
The M U tripping switch has an overload coil so that the con- 
tactors act as circuit breakers. 

Master Control. — With the rapid increase in the current re- 
quired by the motors as the size and capacity of electric railway 
equipment advanced, it became more and more difficult to de- 
sign a controller of the type described above to break continually 



1 


m^ 






<^ 










1 


L^ 




1 

4 


1 , 7/ 

Bab '"^^s JHIB 


'^.'•J^^^^^B 













Fig. 141. — Contactor. 



these large currents. As a result a master controller is often 
found in the motorman's cab, quite similar in principle to the 
large controllers, but designed to control an auxiliary circuit 
only. This auxiliary circuit operates a series of contactors or 
solenoid operated main switches mounted under the car. With 
such a system the contactors may be sufficiently large to control 
the heavy currents safely and little room is required for equipment 
above the floor, not to mention the reduction in the amount of 
heavy cable demanded by such an equipment. The auxiliary 



CONTROL SYSTEMS 



307 



circuit may be a high resistance circuit suppHed from the trolley 
or in some instances it is supplied by a storage battery of about 
14 volts. 

As indicated in the classification on page 300, master control 
systems may be either hand operated or automatic. At present, 
on account of their reliability, flexibility, light weight, simplicity, 
low first cost and maintenance charges, and the fact that the 




Fig. 142. — Type C-94-A controller. General Electric Co., master controller. 



master controller is manipulated in the same way as the type K 
controller, the hand operated types are more popular than the 
automatic types. 

The advantages of master control over main circuit control 
for heavy service are briefly as follows: 

1. Greater safety and reliability. 

2. Each switch may be made a separate element. 



308 ELECTRIC RAILWAY ENGINEERING 

3. It is easy to provide powerful magnetic blowouts for each 
switch. 

4. Flexibility in the arrangement of switch groupings. 

5. Rapidity with which contacts may be ''made" and 
''broken." 

6. Small amount of space required on car platforms. 

7. Heavy cables running from the motors to the car platforms 
are eliminated. 

The disadvantages are: 

1. High first cost. 

2. More complicated. 

With all types of master control a safety device known as 
the "deadman's handle" may be readily provided. In one form 
of this device the main controller handle is turned against a 
spring which throws the handle to the "off" position in case the 
motorman removes his hand. In another form, the pressure 
of the motorman' s hand on a button in the top of the main con- 
troller handle closes a set of contacts which complete the auxiliary 
circuit. This device may be constructed not only to shut off 
the power, but also to apply the air brakes automatically if 
the motorman's hand is removed from the control handle. 

Multiple Unit Control. — There is a demand in elevated, 
subway and heavy interurban service for the operation of a 
number of cars in a single train from the motorman's cab of the 
front car. A marked advance in the design of control equip- 
ment was made, therefore, when the multiple unit control system 
was developed by Sprague. This system not only- embodies the 
use of the master controller explained above, but it permits 
the contactors upon all cars to be operated simultaneously by 
the master controller of a single car, the small auxiliary circuit 
wires alone extending between cars through the agency of flexible 
cables and plug contacts. The equipments are all interchange- 
able so that any car may be made a control car. 

Electro -magnetic Control (Sprague General Electric Multiple 
Unit Control). — In this type of control the main circuit switching 
is performed by electro-magnetic switches. Each switch is held 
closed against a heavy spring by means of a powerful solenoid. 
De-energization of the solenoid causes the switch to open sud- 
denly. The auxiliary circuit is connected through a high resistance 
directly to the trolley. This system of control is manufactured 
in both the hand operated and the automatic types. Fig. 143 



CONTROL SYSTEMS 



309 



represents the wiring diagram of both the main and auxiliary 
circuits of this type of multiple unit control in detail, while Fig. 



/^UA^^^^^v>^^v>iWJAvvl^; 




141 illustrates the contactor with its relay contacts at the bottom 
and its asbestos trough for the circuit breaker at the top. 

Electro -pneumatic Control (Westinghouse Unit Switch Con- 
trol). — The unit switch control is a system developed by an- 



310 ELECTRIC RAILWAY ENGINEERING 

other manufacturing company to meet the requirements of master 
control of single car equipment or of multiple unit control. In 
fact upon one large railway system cars with the unit switch 
control and the Sprague multiple unit control are operating 
interchangeably in the same train. 

The unit switch control differs from the Sprague multiple 
unit system principally in details of operation, the principle of 
the two being the same. Both systems have the main switches 
and reversers located under the car, the operation of these 
switches being controlled by the master controller and an auxiliary 
or relay circuit. In some types of the unit switch system energy 
for the auxiliary circuit is obtained from a 14-volt storage 




Fig. 144. — Unit switch group. 

battery which is carried in the car; in other types the auxiliary 
circuit is energized from the trolley. 

The main switches, Fig. 144, are operated by air pressure 
obtained from the main air brake reservoir, the air valves being 
operated by solenoids which are energized from the auxiliary 
circuit. 

The automatic '^ notching up'^ feature of the unit switch 
system, which may also be secured with the Sprague multiple 
unit control is accomplished by providing the main switches or 
contactors with relay contacts which make the proper con- 
nections in the auxiliary circuit as they open or close. 

The master controller of the automatic unit switch system, 
Fig. 145, is provided with three forward and three reverse notches, 
the function of which will be more clearly seen by referring to 



CONTROL SYSTEMS 



311 



Fig. 146, which is a much simphfied connection diagram. The 
first notch closes the hne switch T and the unit switches a and b, 
thus putting the motors in series with all resistance in circuit. 
This is not a permanent running notch, but the train may be 




Limit Cafl 



Fig. 145. — Unit switch master controller. 



Fig. 146. — Simplified connec- 
tion diagrams for unit switch 
system. 



thus operated at slow speed for switching, etc., for a short 
time. 

The second notch on the controller is the full series running 
position. This closes switch c which has interlocking con- 
tacts which in turn close RRi. The latter switch carries inter- 
locks which close Ri and so on, closing RR2, Ri, RRs, Rs, etc., 
in order cutting out corresponding resistance steps until the 



312 ELECTRIC RAILWAY ENGINEERING 

motors are in series without resistance between trolley and 
ground. 

Notch No. 3 or the full parallel running position closes switch 
d which in turn breaks the auxiliary circuit of h and the latter 
switch opens together with all the resistance switches except 
c. When h has completely opened it causes switches e and G 
to close. When these are fully closed their interlocking relays 
open switch d. When d is again open the circuits through the 
resistance switches RRi, Ri, RR2, etc., are closed consecutively 
until the resistance has again been gradually cut out and the 
motors are finally operating in parallel across the line with no 
resistance. Limit relay switches described above prevent the re- 
sistance switches from closing before the current has decreased 
to its normal accelerating value. This maintains nearly constant 
current during the acceleration period. 

A complete wiring diagram for the unit switch automatic 
multiple unit control system including both auxiliary and main 
circuits will be found in Fig. 147, but because of its complica- 
tion the simplified diagram of Fig. 146 will be found preferable 
for all but detail connections. 

It must be remembered that in all automatic multiple unit 
control systems the power circuit of each car is complete in itself, 
with independent contacts with trolley or third rail. Each car, 
therefore, must have its own limit switch which may be adjusted 
for a different value of current for each car to correspond with the 
equipment upon that particular car. Provision is also made 
for all the switches to open on any one car in case of failure of 
power on that particular car, the switches ''notching up" auto- 
matically when the power is again supplied. The latter feature 
is important with third rail operation in which the power is off 
when passing over each crossing. In order to take care of the 
preceding condition with the hand operated master control 
systems, a train ''bus line" is provided. This line is a heavy 
conducting cable running the length of each car and terminating 
in coupler sockets. As this line is connected directly to the 
trolley base or third rail shoes, all collecting devices on the train 
will be in parallel if the bus line is coupled between cars, and, if 
one current collecting device is resting on a live contact line, 
power will be available on all cars in the train. This bus line 
is now used in connection with practically all automatic control 
systems also. 




-i:;pe 2ai unit switch ucoap 

Fia. 147. — Wiring diagram, unit switch multiple unit control 



{Facing page 312) 



CONTROL SYSTEMS 



313 



Westinghouse PK Control. — To meet the demand for a light 
weight control system embodying the principal features of 
multiple unit and master control for use on stepless and other 
new tj^pes of light weight, low powered, large passenger carry- 
ing capacity cars, the Westinghouse Electric & Manufacturing 
Company has developed a control system known as the PK sys- 
tem. In this system the usual controller case top of a drum 
main circuit controller is replaced by a pneumatically operated 
notching mechanism. This mechanism is controlled by a master 
controller similar to that used with the other types of master 
control. But one main circuit controller is required and it may 
be placed under the car. 

High Voltage Direct Current Control Systems. — In general, 
direct current control systems for trolley voltages ranging from 
1200 to 2400 volts are very similar to those designed for 



Dynamotor 
Change over Switch 1 



Trolley, 

■eoo Volts 




Shunt 
field 
Armatare 
Winding No.2 



Extra Switches 
for 1200 Volts 

Motors, Two of Each Pair in Series 



LoTHP o^M^-/| 

Parallel Connections -= 



Fig. 148. — Schematic diagram for 1200-volt equipment with type HL 
control arranged for half speed operation on 600 volts. 



600 volts. While drum controllers rated for use with a maximum 
line voltage of 1300 volts are on the market, not many of them 
are being used. The higher voltages require better insulation, 
greater ''creepage" surface and heavier parts than are required for 
600 volts. On account of the tenacity of high voltage direct 
current arcs, the final break in the main circuit is usually made by 
operating simultaneously several switches in series. Within 
city limits high voltage direct current interurban railways usually 
operate their cars over the tracks of the low voltage city system. 
One of the many methods of working out the control problem 
for the above conditions is indicated in Fig. 148. When the car 
is operating from the 1200 volt trolley line a dynamotor is used 
to furnish 600 volts to the lights, air compressor and auxiliary con- 
trol circuit. For 600 volt operation the dynamotor change-over 
switch must be thrown. Between the ends of the 600 volt and 
1200 volt trolley lines a short section of dead trolley line is usually 



314 ELECTRIC RAILWAY ENGINEERING 

installed. It is so arranged that this section may be energized 
either from the GOQ volt line or the 1200 volt line, depending on 
the direction in which the car is traveling. The car is run under 
the dead section and the change-over switch thrown to the proper 
position; the dead section is then energized by closing a pole 
switch which connects it with the line ahead. 

Alternating Current Control. — As the principal advantage in 
the use of alternating current motors on the car is the possibility 
of using high trolley voltages and as the alternating current 
motors are best designed for low voltage, i.e., from 200 to 225 
volts, a transformer must be used on the car to reduce the trolley 
voltage to that suitable for the motors. Since taps may be taken 
from the various coils of this transformer to furnish still lower 
voltages useful in starting the car without the resistance loss 
entailed by the resistance type of direct current motor control, 
the principle of alternating motor control differs somewhat from 
those previously explained. 

Alternating current control systems may be either main cir- 
cuit or of the master control multiple unit type. If the former, 
the controller is similar to the K series-parallel drum controller 
with the exception that there are fewer notches, usually five or 
six only, and no series-parallel connections. The magnetic 
blowout coil is also omitted as the alternating current arc is not 
difficult to extinguish without the coil. The various contacts 
made between controller sectors and the stationary fingers 
serve to connect the motors, generally permanently connected 
two in series, to the various taps of the transformer. The 
reversal of the motors is accomplished in the same manner as 
in the type K controller, the reverse cylinder reversing either the 
armature or field connections. 

With the alternating current master control the principle of 
operation is the same as before. The magnetic cores of the re- 
verser and contactors must, however, be laminated for use on 
alternating current circuits. 

In order that connections may be changed from one transformer 
tap to another without opening the circuit it is necessary to close 
a local circuit through a portion of the transformer winding; i.e., 
if special precautions are not taken a short circuit will be formed 
in a portion of the transformer coil as two taps of the transformers 
are connected to the same motor terminal. In order to avoid 
this difficulty the current is reduced in the local circuit by means 



CONTROL SYSTEMS 315 

of ''preventive" resistance or reactance leads as in the case of 
the single-phase motor. 

The transformers used with the alternating current motor 
equipments have been standardized for 3000, 6000, and 10,000 
volts trolley potential and are connected directly between trolley 
and ground. On account of the insulation strains liable to be 
imposed on the motor windings when auto-transformers are used, 
the present tendency is toward the use of two-winding trans- 
formers, the secondaries of which are provided with a number 
of taps. The transformer is mounted under the floor frame of 
the car. 

While the adjustable ratio transformer control system works 
well for single-phase railway motors, polyphase motors require a 
different system. Where wound rotors are used and but one 
running speed is required, a type of rheostati6 control is used. 
By arranging the stator windings of the motors so that they may 
be connected to form different numbers of poles around the stator 
periphery other running speeds may be obtained. A controller 
whose main drum cuts resistance in or out of the rotor circuits 
as may be desired and whose auxiliary drum performs the func- 
tions of reversing switch and pole changing switch meets the re- 
quirements where more than one running speed is necessary. 
As three-phase motors are used only on heavy cars or locomotives, 
the master control system is used almost universally; the con- 
trollers just mentioned simply control the auxiliary circuits which 
operate the switches in the main circuits. Liquid resistances are 
often used for the starting resistances of three-phase locomotive 
motors. 

Combined Alternating and Direct Current Control. — As 
previously pointed out, it is desirable that most alternating current 
interurban roads operate cars to the heart of the terminal cities. 
They must, therefore, be able to operate upon both alternating 
and direct current. In order that the control equipment may be 
fitted for either, some changes in detail must be made and a 
considerable complication of circuits results. The various parts 
of the apparatus such as controller, reverser, contactors, etc., are 
used in common by the two systems. A number of changes in 
connections, however, must be made in shifting from one system 
to another. These are principally as follows when changing from 
alternating to direct current operation: 

Change transformer taps to resistance taps. 



316 ELECTRIC RAILWAY ENGINEERING 

Change main fuses or circuit breakers. 

Change Hghtning arresters. 

Introduce the magnetic blowout into the circuit. 

Change hghting and heating circuits. 

Reconnect fields of air compressor motor for series operation. 

In order that these changes may be made in one operation 
the cables involved are connected to a second control drum 
similar to the main controller. This is styled the ''commutating 
switch," the preceding changes being made by a simple move- 
ment of the handle. This change may also be made auto- 
matically at full speed by providing a release for the switch 
when no potential is supplied so that it will open as the car 
reaches an insulated section in the trolley between the alternat- 
ing and direct current systems. The switch is designed to 
reset automatically in the opposite direction as the direct 
current trolley is reached, and vice versa. 

As may be inferred from the foregoing, an addec complication 
enters into the problem in operating the air compressor for the air 
brake system. In some installations a motor generator set of 
small capacity is installed to furnish 550 volts direct current 
when supplied with alternating current from the transformer. 
The standard direct current air compressor may then be used. 
Another method more often found is to design the compressor 
motor for both alternating and direct current, connecting the 
field coils in parallel for the former supply and in series for the 
latter. 

Whereas the combination of the two control systems upon 
one car adds considerable complication, as will be seen frojn Fig. 
149 which represents the complete wiring diagram for an 
alternating current direct current control equipment, and al- 
though the first cost and maintenance charges are necessarily 
increased thereby, the added advantages of alternating current 
operation apparently warrant such an installation, for several 
roads are successfully operating such an equipment. 

Regenerative Braking. — Since polyphase motors will act as 
generators if run above synchronous speed, regenerative braking 
does not introduce any complications into the system which 
controls them. Where series motors are arranged for regen- 
erative braking, additional points on the controller and addi- 
tional contacts are required to take care of the auxiliary windings 
or connections on the motors. 




Fig. U9.-Wiring diagram, A-C. D-C. control. 



CONTROL SYSTEMS 317 

Controller Selection. — Since the successful operation of 
railway motors depends largely on the reliability and effective- 
ness of the control apparatus, it is evident that the problem of 
controller selection is one which must be studied with care. 
Direct current main circuit controllers rated at 600, 750, and 1300 
volts maximum are standard products. The capacity of a 
controller is usually rated in terms of the maximum motor 
horse power which it can control without undue heating of 
contacts and other current carrying parts. Master controllers 
are built for all voltages, capacities and kinds of current. 

In the selection of a controller the following are some of the 
more important points which should be considered: 

1. Nature of service, i.e., voltage of line, kind of current, 
number of cars in train and weight of cars or locomotives. 

2. Capacity of motors. 

3. Number and kind of motors. 
.4. Ground or metallic return. 

5. Available floor space on platform. 



CHAPTER XXIV 
BRAKES 

The problem of stopping a car is quite as important as that 
of acceleration. Since the kinetic energy of the car must be over- 
come in a very few seconds the power required for braking 
the car is usually many times that required for accelerating. 
Whereas the rate of retardation and energy required during 
the braking period have been already considered, it is now 
necessary to study the braking forces more in detail, as well as the 
various types of equipment which have been designed for the 
production and control of such braking forces. 

Electric cars must be accelerated and retarded by virtue of the 
frictional force between the wheels and the rails. As this force 
is proportional to the weight on the wheels, the available force is 
conveniently found from the ratio of horizontal pull in pounds 
necessary to slide the wheels on the rails to the pressure between 
wheels and rails. This ratio is commonly termed the coefficient 
of friction. It has been found to vary with the materials in 
contact and the velocity and the length of time during which the 
force is applied. 

While many different devices have been tried out in practice 
for producing the necessary frictional forces to stop a car, the one 
which is now almost universally used in both electric and steam 
railroad service is the application of a brake shoe, usually of cast 
iron or a combination of cast iron and other materials, to the 
treads and flanges of the car wheels by means of either hand or 
air pressure transmitted through the agency of a carefully pro- 
portioned system of levers. 

Coefficient of Friction. — An experimental study of the coeffi- 
cient of friction between cast iron brake shoes and steel wheels 
under practical service conditions was made by Galton and 
Westinghouse in 1878, and the results of these tests, published in 
the 1879 proceedings of the Institution of Mechanical Engineers, 
which are given in the following tables, have been ever since con- 
sidered as classic, the few later tests which have been made 
making little if any change therein. 

318 



BRAKES 



319 



Table XXXIV. — Coefficient of Frictiox at Various Speeds with Cast 
Iron' Brake Shoes on Steel Tires 





AVlocity 


Coefficient of friction 


No. of tests 

from which 

mean is taken 


M.p.h. 


Ft. per sec. 


Extreme 






Max. 


Min. 


Mean 


12 


60 


88 


0.123 0.058 


0.074 


67 


55 


81 


0.136 


0.060 


0.111 


55 


50 


73 


0.153 


0.050 


0.116 


77 


45 


66 


0.179 


0.080 


0.127 


70 


40 


59 


0.194 


0.088 


0.140 


80 


35 


51 


0.197 


0.087 


0.142 


94 


30 


44 


0.196 


0.098 


0.164 


70 


25 


36.5 


0.205 


0.108 


0.166 


69 


20 


29 


0.240 


0.133 


0.192 


78 


15 


22 


0.280 


0.131 


0.223 


54 


10 


14.5 


0.281 


0.161 


0.242 


28 


7.5 


11 


0.325 


0.123 


0.244 


20 


Under 5 


Under 7 


0.340 


0.156 


0.273 




Just moving. . . 


Just moving. . . 




. 330 



Table XXXV. — Effect of Elapsed Time on Coefficient of Friction 



Speed, 
m.p.h. 



Coefficient of friction 



Start I After 5 sec. ! After 10 sec. j After 15 sec. After 20 sec. 



20 
27 
37 

47 
60 



0.182 


0.152 


0.133 


0.171 


0.130 


0.119 


0.152 


0.096 


0.083 


0.132 


O.OSO 


0.070 


0.072 


0.063 


0.058 




From the above tables the maximum pressure to be appUed 
to the brake shoes may be determined under the various service 
conditions in order to provide the required frictional tangential 
force. To determine what the Kmits of the latter are the coeffi- 
cient of friction between wheels and rail must be known. This 
value varies widely with the condition of the rail, but may be 
safeh^ assumed from 0.15 to 0.30 when the rail is wet and dry 
respectively. These latter values are coefficients of static friction 
which are greater than dynamic friction if other conditions are the 
same. For if the wheels are rolling, there is no relative sliding 
between wheels and rails and the frictional force to be considered 



320 ELECTRIC RAILWAY ENGINEERING 

is that necessary to start one body from rest upon the other and 
not that lesser force necessary to keep one body in motion upon 
the other. The maximum Hmit of brake shoe friction is now at 
once apparent, for it must not exceed the static friction between 
wheels and track. If it were to exceed that value, the brake 
shoes would '4ock the wheels" and the latter would ''skid" on 
the rails with lessened retardation because of the lower value of 
dynamic friction thus suddenly brought into play between wheels 
and track. In fact this is the cause of the sensation often expe- 
rienced by passengers upon a car who, when barely accustomed 
to the slowing down of the car during the braking period, suddenly 
feel the car apparently ''shooting forward" as the wheels begin to 
slide on the track. The decreased frictional resistance offered 
to the motion of the car under these conditions permits of little 
if any control of the car by the motorman and serious accidents 
often result therefrom. 

Theoretically, cars should be equipped with braking apparatus 
which will be able to approximate as nearly as possible this maxi- 
mum value for emergency stops, but since the braking force with 
hand brake equipment depends upon the strength of the motor- 
man and with air brake equipment upon the variable air pressure, 
it is usually possible to "skid the wheels" on the average car if 
the brakes are applied too forcibly. Further, since Tabl-e XXXIV 
shows that the friction between brake shoe and wheel increases 
as the speed decreases during the braking period, a force applied 
to the brake shoes when braking is commenced, which is slightly 
less than that necessary to lock the wheels, may become suffi- 
ciently great to produce that result at lower speeds for the reason 
that the static friction between wheels and track remains con- 
stant. Every experienced motorman understands the results 
of such an application of brakes and releases and reapplies the 
braking pressure with less and less intensity as the car comes to 
a stop. Failure to do this results in too sudden a stop for com- 
fort, a severe chattering of the brake rigging and possible skid- 
ding, and incidentally marks an inexperienced or careless 
motorman. 

Another factor which must be taken into consideration in 
stopping a car comfortably and safely is the condition of the track. 
It is a peculiar fact that with a very thin film of water on the 
rail due to a slight shower, the friction is greatly reduced over 
that of a dry rail or even a thoroughly wet rail. Again, the 



BRAKES 



321 



crushing of leaves or weeds on the tread of the rail or too generous 
a suppl}^ of track grease often makes it impossible to stop on a 
section of track thus affected without the use of sand. Cars 
have been known to slide down long hills with tracks thus covered 
while the motorman was utterly powerless to reduce the speed, 
even with the reversal of the motors. Most roads, therefore, 
provide a generous supply of sand on each car not only, but 
require the track repair crew to keep the track free from leaves, 
grass and weeds. 

Braking Forces. — If the car is to be stopped by the applica- 
tion of pressure to the brake shoes bearing upon the car wheels 
as is ordinarily the case, it will be noted at once that the forces 




Fig, 150. — Special brake shoe suspension. 



tending to move the car forward and those applied as resistances 
to stop the motion do not lie in the same horizontal plane, the 
former acting at the center of gravity of the combined loaded car 
body and trucks and the latter at the contact between wheels 
and rails. The result is easily seen to be a tendency to raise the 
rear of the car from the track, the forces acting at the center of 
gravity of the car having a moment about the front truck. In 
addition, there is a tendencj^ for the rear wheels of each truck to 
lift from the track for the reason that the forces at the king pin 
and center of gravity of the truck have a moment about the front 
wheels. The resulting effect is that the pressure is lessened 
between car and rails at the rear and the static friction depended 

21 



322 



ELECTRIC RAILWAY ENGINEERING 



upon for braking is thereby reduced. Either the braking pressure 
must be reduced upon the rear truck over that of the front truck 
and that of the rear wheels of each truck over that of its front 
wheels or else all braking pressures must be lowered conside ably 
below that possible at the front end of the car. That the braking 
pressures on the rear truck cannot be made less than those of the 
front truck by any change in the leverages on the car in the case 
of double end cars is obvious. With single end interurban cars 
such provision is often made. There is, however, a method of 
hanging brake shoes with the supporting link of the brake shoe out 
of line with the tangent to the wheel at the center of the shoe 
which will vary the pressure between shoe and wheel with the 




Fig. 151. — Brake shoe suspension with excessive angle. 



direction of operation of the car. This may be illustrated by 
referring to Fig, 150 where the brake shoe hanger is 5 deg. out of 
line with the tangent. With the car moving toward the right, 
the frictional force at the shoe is balanced by a force of com- 
pression in the hanger plus a force normal to the car wheel 
proportional to the sine of 5 deg. This is added directly to the 
brake shoe pressure. If the car be operating toward the left, 
thus making the wheel shown in the figure the rear wheel of the 
truck, the frictional force produces a tension in the brake shoe 
hanger and a force proportional to the sine of 5 deg., tending to 
reduce the pressure exerted by the brake rigging. Whereas this 
effect may be increased by increasing the angle between brake 



BRAKES 



323 



shoe hanger and tangent, too great an increase of this angle tends 
to bind the shoes upon the wheel as in the case of a toggle joint, 
causing chattering of the brake rigging and flat wheels. Such a 
condition, often found on car trucks, is illustrated in Fig. 151 
where the angle has been increased to 30 deg. 

In order to determine the concrete value of the resultant 
weight upon each wheel of a car, it is necessary to analyze all the 
forces acting thereon as outlined in Fig. 152 and to balance the 
moments of the forces about any single point as in any problem 
in mechanics. A sufficient number of equations will result to 
permit the weights (TFi), (^^2), (TFa) and (TF4) to be calculated 
and the corresponding frictional forces {Fi), (F2), (F3) and (F4) 
determined through the agency of the coefficient of friction. In 
determining the above equations, it must be remembered that 



Direction of Motion 




Fig. 152. — Forces acting on car during braking. 



the rotative inertia of the car wheels, axles, and motor arma- 
tures must be overcome in stopping the car as well as the trans- 
lational inertia of car and trucks. 

Whereas, the method above outhned will result in a very ac- 
curate analysis of the various weights and forces involved, it 
would be seldom indeed, that the electrical engineer would make 
such a calculation before writing specifications for car equipment. 
The effect of reduction of pressure at the rear of the car may be 
taken roughly at 15 per cent, and the brake rigging designed for a 
resultant brake shoe pressure corresponding to 85 per cent, of 
the actual static weight on w^heels. 

Braking Equipment. — It has been previously stated that the 
hand and air brake systems are now almost universally used in 
electric railway service. The former is used alone upon small 
city cars, while both systems are universally applied to the 



324 



ELECTRIC RAILWAY ENGINEERING 



heavier city, suburban and interurban equipment. Where both 
are used the same brake rigging is installed for both, the lever- 
ages in the case of the hand brake being greater to make up for 
the relatively small pull the motorman can exert as compared 
with the air pressure of the brake cylinder. A typical brake 
rigging installation may be seen in Fig. 153, the operation of 
which will be self-explanatory if it be stated that the piston of 
the air brake cylinder is forced forward by air pressure, when 
the proper valve position is provided by the motorman, just as 
the piston of a steam engine is operated. The principal di- 
mensions of the various parts of the equipment of several inter- 
urban cars of the Middle West are given in Table XXXVI, all 
of which refer to Fig. 153. The ratio between brake shoe pres- 
sure and brake cylinder pressure may be readily obtained from 



PiXed Poini 




Fig. 153. 



Brake Cylinder 

-Typical brake rigging. 



the following equations. With this ratio known the air brake 
pressure per square inch of piston area may be quickly deter- 
mined for various desired brake shoe applications. 

Table XXXVl. — Dimensions of Air Brake Equipment 



Interurban 






Dimensions of levers 


in inches 






car 


A 


■ 


° 


D 


E 


F 


° 


1 


10.5 


9.0 




5.0 


16.0 


4.0 


13.0 


2 


9.5 


9.5 




7.0 


18.0 


7.0 


18.0 


3 


12.0 


23.0 




6.0 


16.0 


5.0 


15.0 


4 


11.0 


17.0 


35 


5.0 


12.5 


5.0 


12.5 



Let (P) represent the total force on the piston of the brake 
cylinder and designate the resultant forces in the various links 
by the letter.s appearing upon the links in Fig. 153. 

P = Air pressure X area piston (106) 



BRAKES 



325 



From the ratios of lever arms the following equations may be 
derived : 



2 2B 



T = 
V = 

r = 



Y(D + E) 

D 
YE 
D 

V(F + G) 
G 



(107) 
(108) 
(109) 
(110) 



If the ratio between total pressure exerted by all brake shoes 
to brake cylinder pressure be signified by {R). 

4(r + r) 



R (for a double truck car) = 



(111) 



Substitution in the above equations of values for the four cars 
in Table XXXVI results in the forces Hsted in Table XXXVII 
with a 10 in. cylinder and maximum air pressure of 70 lb. per 
square inch. 

Table XXXVII — Forces Acting in Air Brake Equipment 









Pounds 






Interurban 












car 


















P 


w 


Y 


T 


V 


T' 


R 


1 


5,497 


6,400 


3,200 


13,450 


10,250 


13,400 


19.6 


2 


5,497 


5,497 


2,748 


9,830 


7,080 


9,830 


14.4 


3 


5,497 


2,860 


1,430 


5,250 


3,820 


5,100 


7.54 


4 


5,497 


3,550 


1,775 


6,210 


4,430 


6,210 


9.06 



From the above table it will be seen that the multiplying power- 
of the brake levers on four interurban cars taken at random 
varies from 7.5 to 19.5. 

It should not be forgotten that the above forces are based upon 
an emergency application of air of 70 lb. pressure which is seldom 
used. For an ordinary service application the forces would 
average less than one-half the above values. 

A further calculation may be made from Table XXXVI which 
is of value in determining the adequacy of the equipment for the 
service. Car No. 4 in this table weighs in the neighborhood of 
25 tons. The total brake shoe pressure exerted on all wheels 
with a 70 lb. application of air is 

8 X 6210 = 49,680 lb. 



326 ELECTRIC RAILWAY ENGINEERING 

Ratio of total brake shoe pressure to weight of car is 99.2 per 
cent. If the coefficient of friction were the same between shoe 
and wheels that it is between wheels and rails it would be possible 
to skid the wheels with an application of air slightly above 
70 lb. 

Brake Rigging. — The levers by means of which the braking 
force is transmitted from hand brake or brake cylinder to brake 
shoes are of heavy strap iron linked together with steel pins 
provided with cotter pins and supported from the under frame of 
the car by means of strap iron stirrups. Links in tension are 
usually constructed of 1 in. round iron rod. The circle bar 
between links (F) and {W) Fig. 153 is provided with the truck 
together with a clevis which may be welded to rod (TF) and 
which is so designed as to slide on the circle bar as the trucks 
swing with respect to the car body when turning a curve. 

The hand brake consists of the familiar vertical ratchet crank 
or wheel in the motorman's cab which winds up a chain under 
the car vestibule, this chain exerting a tensile force at E, 
Fig. 153. 

Straight Air Brake Equipment. — The air brake equipment 
in its simplest form consists of a motor driven air compressor, a 
storage reservoir, a brake cylinder, a governor, two engineer's 
valves with gauges for double end equipment, a system of levers, 
complete piping equipment and usually one or more air whistles 
to act as signals. Fig. 154 represents the apparatus above out- 
lined. The compressor, reservoir, brake cylinder and piping are 
supported from the underframe of the car. The governor is 
often placed on the car floor under one of the end seats, while the 
remainder of the equipment is in the motorman's cab. 

The air compressor is a direct connected pump and direct 
current 550 volt series motor connected between trolley and 
ground with only a snap switch, the governor switch and a fuse 
in circuit. The trolley connection is made between circuit 
breaker and trolley so that the compressor will not stop when 
the circuit breaker opens. 

The governor is a pneumatically operated switch which can be 
adjusted to close the compressor circuit and thereby start the 
compressor when the air pressure falls below a predetermined 
value and which will automatically stop the compressor when the 
pressure reaches the maximum value desired. While there is a 
considerable range for which the governor may be adjusted, it 



BRAKES 



327 



is generally set to operate at about 70 and 90 lb. per square inch 
respectively. 

The motorman's valve is of the three position type. The 
operating handle, when moved to the ''service" position opens 
the valve between reservoir and brake cylinder and applies the 
brakes. The extent to which the handle is moved in this direc- 
tion and the time during which it is left there determine the 



« 


9 






Ik 


■ ft ^ 




i 


^gr 




^•^ 


^ 


c 


t 



Fig. 154. — Straight air brake equipment. 



pressure applied to the brake shoes. If it be desired to retain 
this pressure in the brake cylinder the handle may be moved to 
the ''lap" position where all valves are closed. The handle may 
be removed only when in this position. By throwing the handle 
to the position opposite to that of "service" into the exhaust" 
notch the air in the brake cylinder escapes to the atmosphere 
and the brakes are released. It is a rather unfortunate fact that 



328 



ELECTRIC RAILWAY ENGINEERING 



two types of air brake valves apply the air with opposite move- 
ments of the valve handle. This is rather confusing to motor- 
men accustomed to one method when changing to another road 
using the other system. 

Emergency Straight Air System. — One of the disadvantages 
of the ^'straight air" system is the length of time required to 
apply the brakes due to the relatively long length of pipe through 
which the air must flow from the reservoir to the brake cylinder. 
This is, of course, especially objectionable in an emergency ap- 



Gage Whistle 




Fig. 155.— Emergency straight air brake system. 



plication. To overcome this objection for emergency stops 
and at the same time to avoid the complication and high first 
cost of the automatic system, the comparatively new system 
known as the '^ emergency straight air brake system" has been 
evolved. 

This sytem adds an emergency valve and reservoir line to the 
equipment and provides emergency application and release 
positions on the motorman's valve. When the valve is thrown 
into emergency position it allows the pressure of the reservoir 
line which is higher than that in the emergency valve to compress 



BRAKES 



329 



a spring in the latter and thereby allow a direct passage of 
reservoir air into the brake cylinder. Connections with the 
train line and reservoir lines are also simultaneously cut off. 
The application of the brakes on trailers is made possible by the 
addition of an auxiliary air reservoir, emergency valve and 
reservoir line to the equipment necessary for '^ straight air" 
braking. 

In order to release the brakes after an emergency application, 
the emergency valve must first be returned to its normal position 
by recharging the reservoir line to reservoir pressure, where- 
upon the brakes may be released as from a service application 



Conductor's 
Valve 



Brake Cylinder 




Fig. 156. — Emergency straight air brake for trail cars. 



by exhausting the air from the train line. The equipment 
necessary for motor and trail cars is indicated in Figs. 155 and 
156 respectively. 

Automatic Air Brake Equipment. — Contrasted with the 
above '^ straight air brake equipment" which is applicable to 
single cars only the ^'automatic air brake equipment," Fig. 157, 
similar to that used on steam trains is often found on electric 
lines, especially in elevated, subway, and heavy interurban 
service where two or more cars are coupled together. The 
principal difference between this system and the one previously 
described is the addition of a second or auxiliary storage reservoir 
and the use of a 'Hriple valve." A 'Hrain line" or continuous 



330 



ELECTRIC RAILWAY ENGINEERING 



pipe under air pressure is provided throughout the train, rubber 
hose coupHngs with patented air tight knuckle joints permitting 
the ready closing of the line when shifting cars. The ''triple 
valve/' which is the vital part of the entire system, consists of a 
piston valve ordinarily balanced in a mid position by the auxiliary 
reservoir pressure on one side and the ''train line" pressure on 
the other. When the motorman's valve is in the "service" 
position the train line is momentarily opened to the atmosphere 
and its pressure reduced sufficiently to cause the auxiliary reser- 
voir pressure to move the triple valve piston to such a position 
as to admit air from the auxiliary reservoir to the brake cylinder 
and apply the brakes. This occurs on every car of the train. 




To T rolley 
{Switch 



Switch 



-Motorman's Brake Valve 
-Slide Valve 
^Feed Valve 



Pump Governor 



Whistle 
Keservoir 




Safety Valve 



Main Reservoir 



Duplex Check Valve 



Brake Cylin ders^ /'Auxiliary Keservoir 




Triple Valve 



Air Strainer 

Fig. 157. — Automatic air brake system 



To release the brakes the motorman's valve in the "exhaust" 
position allows air to flow from the main reservoir to the train 
line and raise its pressure so that the triple valve is again balanced 
and the brake cylinder opened to the atmosphere. One of the 
most valuable features about this equipment is the fact that any 
leakage or breaking apart of cars, etc., which will reduce the 
pressure in the train line will set the brakes upon all cars of the 
train. 

Quick Action Automatic System. — The automatic air brake 
as above described is applicable to trains up to about five cars in 
length. For the longer trains, however, the reduction in train 
line pressure requires an appreciable time to be felt throughout 



BRAKES 331 

the length of the train. The resulting effect of some cars of the 
train braked with others free causes severe strains on the draft 
rigging, not to mention inconvenience to passengers. The 
''quick action automatic air brake system" is therefore applied to 
the longer trains. This is similar to the other with the exception 
that the '^ triple valve" is so designed as to feed both auxiliary 
reservoir and train line pressure into the brake cylinder. This 
procedure not only causes each car to aid in quickly reducing 
the train Une pressure throughout the train, but it decreases the 
drop in train line pressure which must be produced at the head 
car. In other words the action is cumulative throughout the 
length of the train. 

In both the automatic systems the motorman is provided with 
a duplex gauge indicating both train Une and main reservoir 
pressure. In the straight air brake system either a single gauge 
hand is provided to denote the reservoir pressure or two indica- 
tions are given, one above outHned and in addition a second 
hand to show the pressure appHed to the brake cylinder. 

Friction Disc, Electric and Track Brakes. — INIany types of 
special braking de\dces have been invented and tried out, involv- 
ing friction discs bearing upon the planed inside surfaces of car 
wheels, magnetic brakes supplied with energy either from the 
trolley or the car motors used as generators, and track brakes 
consisting of shoes bearing upon the rail instead of the car wheels 
and often designed to grip the head of the rail with a variable 
pressure. While some of these devices have served admirably 
in special instance, especially as an additional safety device upon 
severe grades, they are not in sufficiently general use to w^arrant 
detailed description. 

Reversal of Motors. — A method of stopping cars in cases of 
emergency, known as '^ reversing" consists in throwing the re- 
verse lever to the reverse position and applying power to the 
extent of one or possibly two series notches of the controller. 
This, of course, tends to operate the car in the reverse direction 
and not only stops the car with a sudden jolt but is likely to 
damage the car equipment. It is therefore seldom resorted to, 
but in case of failure of the brake rigging or to avoid a colHsion, 
it is sometimes a valuable protection. 

Motors used as Generators. — As a last resort, with no power 
supplied to the car, and with brake rigging damaged, there is 
yet another method of stopping the car. The reverse lever may 



332 



ELECTRIC RAILWAY ENGINEERING 



be thrown into the reverse position and the controller handle 
swung into one of the parallel notches. The resulting connection 
causes one motor to operate as a generator, driven by the inertia 
of the car, thus supplying the other motor with power tending 
to operate the car in the reverse direction. This method may, 
of course, be used if the power supply be present by throwing the 
circuit breaker to the open position. 




With either of the above methods involving the use of electric 
power in stopping the car, great care must be taken not to skid 
the wheels as this condition prevents a prompt stop not only, but 
is likely to flatten the wheels as well. 

Regenerative Braking. — Closely allied with the method of 
stopping a car last discussed is that of ''regenerative braking" 



BRAKES 



333 



in which all motors of the car are so connected that they may 
act as generators delivering electrical energy to the distribution 
system. Although this system of braking is seldom installed for 
the sole purpose of stopping or controlling the speed of trains on 
down grades, it has been used to advantage in several instances 
discussed in the previous chapter and has been found of sufficient 
value to warrant the extra complexity of control circuits involved 
therein. 




3 4 5 

Seconds 
Fig. 159. 



Brake Tests. — It is often of great value to know the time and 
distance required in which to stop cars of various weights operat- 
ing at different speeds. This is particularly true in case of 
accidents and court litigation. Whereas these facts may be 
predetermined mathematically as has been previously pointed 
out, the actual test of a car in service is often required as well. 

In order to carry out such a test thoroughly, it is necessary to 
provide a method of determining speed of car, time between 
brake signal and stop and distance travelled during this period. 



334 



ELECTRIC RAILWAY ENGINEERING 



It is also well in some cases to know the air brake pressure, the 
amount of wheel skidding and the motor current in case either 
of the reverse methods are used. 

One of the most satisfactory methods of determining the speed 
at any instant is by means of a magneto generator, driven from 

120 
100100 

w 

90 90 CM 

80 80 16 

( 

70 70 14 

60 60 13 

50 50 10 

40 40 8 

30 30 G 

30 30 4 

10 10 3 



01334567 
Secoada 
Fig. 160. 

the car axle, the voltage of the generator read from a voltmeter 
in circuit being directly proportional to speed. 

The distance traveled during the braking period may be 
roughly determined from the revolutions of the car wheel or a 
similar wheel driven from the car axle, which may be caused to 
make electrical contacts every revolution. If any skidding 
occurs, this method becomes valueless. A method which has 
worked admirably in recent tests at Purdue University is to give 



























/ 


\ 


GENERATED MOTORS 

FROM 

FULL PARALLEL POSITION 








/ 


\ 










\ 




A 


^ 


J Current per Motoi 






\ 




1 


v^ 


\l 














( 

[ 












y 


) Actv 


al Dis1 


ance 






\ 




















) 






V 


ieed 














< 






\ 

c 


\ 






















\ 


<-- 


i 


) Dista 


ice 






^ 






/ 


/ 


\ 
















A 


(^ 




___\ 


V 


xRetar 


3ation 








^ 


r" 








\ 











BRAKES 



335 



the braking signal by means of a revolver from which a ball is 
shot beside the track, thus marking the start of the braking test 
very accurately. The distance required to stop may then be 
measured along the track from this point with a steel tape. 

All of the data of the test may readily be arranged for an auto- 
matic graphical record upon a single paper chart, thus illustrating 
clearly the desired values at any given instant. 

The results of such tests are best shown by curves similar to 
those of Figs. 158, 159, and 160 which represent braking tests 
made with the Purdue Universitj^ Test Car^ of approximately 
25 tons weight equipped with brake rigging designated as car 
No. 4 in Table XXX VI. While it is believed that these figures 
are in general self explanatory, especial attention should be 
called to the amount of skidding which took place in the stop by 
means of generated motors, Fig. 160, and also to the fact that 
the speed time curve is seldom a straight line as is assumed in 
theoretical calculations. The error in such an assumption, 
however, is obviously small. 

The results of all the tests made upon the above car are given 
in some detail in Table XXXVIII and may prove of some value in 
approximating possible stopping time and distance under other 
conditions. 

T.\BLE XXXVIII.— Braking Tests 



Kind of stop 


Air press., 
lb. per 
sq. in. 




Dis- 
tance 
skidded 
feet 


Decelera- 
tion, 
m.p.h.p.s. 


Speed, 
m.p.h. 


Current 

per 
motor, 
max. 




Max.' Avg. 


Max.' Avg. ' Max. Avg. 


Emergency 


65.0 


56.2 


12.5 


320.0 




2.3 


2.06 


23.0 


12.75 










6.0 


70.7 


33.2 1 3.1 


2.14 


15.0 


8.3 


116.5 










Gen. motors and 






4.0 


45.3 


8.1 


3.0 


2.5 


12.0 


7.0 


110.0 
















5.0 


100.0 


100.0 


3.6 


3.6 


18.0 




165.0 










Ordinary service . . . 


42.0 


28.0 14.0 


220.0 


i 


1.65 


1.41 


22.5 


11.3 




Service 30 lb. air . . 


30.0 


25.6 


18.0 


396.0 




2.6 


1.17 


23.0 


13.0 


Service 40 lb. air.. . 


38.0 


31.3 


9.0 


268.0 




2.2 


1.85 


19.0 


8.7 




Service 60 lb. air... 


57.5 


46.8 


7.0 


181.8 




3.0 


2.64 


21.0 


12.4 




Service 70 lb. air. . . 


60.0 


42.9 


6.0 


193.8 




6.253.15 


22.0 


12.2 



^ Thesis, Purdue University, 1911, by Luhrman, Blaschke and McLean. 



CHAPTER XXV 
CAR HOUSE DESIGN 

As the modern car house not only provides storage for the 
rolHng stock, but also furnishes room for inspection and repairs 
and often includes the shops and offices of the railway company, 
much thought must be given to its location and design. 

Location. — Too often a lot for a car house is secured before 
the size or requirements of the latter are determined, thus re- 
quiring that the car house and track layout be fitted to the lot. 
This procedure results in a limited and unsatisfactory design. 
A site of sufficient size for all the above functions of the car house, 
with proper consideration for future growth, should be selected 
in the most convenient section of the city from an operating 
standpoint. Care must be taken to make sure that all necessary 
track privileges may be obtained from the city authorities before 
the site is finally purchased. 

In the case of the interurban car house, a location for the latter, 
together with the shops, offices and often the power house or 
substation is selected at about the middle of the line, although 
where the interurban road is operated by the company controlling 
the traction systems of the terminal cities the cars may be handled 
by the city car houses. This plan often offers the advantages of 
lessened fire risk, smaller dead mileage of cars, improved freight 
and express accommodations and better or more congenial homes 
for employees. For the advantages to be gained by locating near 
the power house, as well as for an outline of many considerations 
to be taken into account in deciding upon the proper location, 
reference should be made to Chap. XVI. 

The fire risk of a car house is great and abundant water supply 
and other fire protection should be available not only, but care 
should be taken to avoid all fire risk from adjoining buildings. 
The subsoil should be examined with a view toward determining 
the foundations and piling necessary, although with the lighter 
and more equally distributed weight of the car house this is not 
such. a vital factor as with the power station. Good drainage 

336 



CAR HOUSE DESIGN 



337 



and suitable sewer connections should, however, be available or 
easily provided. 

Layout of Tracks. — One of the first questions to be decided 
is the percentage of total cars owned for which cover shall be 
provided. This is a question upon which railway managers 
differ widely. At the 1907 Convention of the American Street 
and Interurban Railway Association a committee appointed to 
investigate this question assumed the case of a car house accom- 
modating 84 cars under cover as compared with a similar design 
capable of housing but one-third this number. The estimated 



Dispatcher! 
Conductors s 




Fig. 161. — Baltimore Park terminal car house. 



costs were $105,000 and $45,000 respectively. With fixed charges 
at 12 per cent., this represents an annual saving of f 7,200 or $85 
per car. A study of the requirements of this road showed that 
all cars not in service between 6 a.m. and midnight could be 
housed by the small structure and of course this would involve 
different cars on different days. The larger car house and the 
increased annual outlay includes simply the ability to house two- 
thirds more cars from midnight until 6 a.m, Since the $85 per car 
will nearly provide for repainting and varnishing a car each year 
and as the added deterioration of the car during this period of 
day when out of service is not great, this particular case seems to 

22 



338 



ELECTRIC RAILWAY ENGINEERING 



favor open storage. Opposed to this evidence probably the most 
important argument for complete car storage is the fact that the 
equipment will certainly receive better attention from inspectors 
and repair crew if all cars are stored within the car house, 
especially in bad weather. 

The next question of importance is whether a single or double 




Fig. 162. — Typical car house track plans. 



end house is desired. The latter type provides more ready 
movement of cars through the house and aids greatly in clearing 
the house in case of fire. Where a whole block or two inter- 
secting streets are available it is often customary to form an 
operating loop through the car house for the cars when in regular 
service with regular inspections as they stop over the inspection 
pits. A rather complicated example of this construction is 



CAR HOUSE DESIGN 



339 



shown in the plan view of Fig. 161, representing the Park 
Terminal car house in Baltimore. The principal objections to 
the double end arrangement are the difficulty in keeping tracks 
clear for through operation, the large amount of special track 
work required and the added difficulty in heating. 

Whichever of the above designs is decided upon, depending 




Fig, 163. — T3^pical car house track plans. 

largely upon local conditions, the problem remains so to connect 
the various tracks of the car house with those of the main line 
that the greatest possible flexibility of car movements within the 
yard may be had without interference with main line traffic and 
without obstructing the main track with more special work than 
is absolutely necessary. Figs. 162 and 163 illustrate several 
typical methods of solution for this problem. Case (A) intro- 



340 ELECTRIC RAILWAY ENGINEERING 

duces several switches into one of the main tracks, but makes no 
connection with the second main track. A more flexible arrange- 
ment is shown in Case (B) where a cross-over is provided to the 
second main track in addition to one located in the car house. 
The latter is often found very useful, but its installation depends 
very much upon the availability of the special work in front of the 
car house for switching purposes. If the special work in the 
main line be objected to, Case (C) may offer a satisfactory solu- 
tion, requiring necessarily more yard room. The design of Case 
(D) uses an extra or '^gauntlet" track in the street for switching, 
while (E) is similar to (B) with the exception that the operating 
tracks are on the right of the storage house. If space will permit, 
(F), Fig. 163, offers an ideal arrangement, allowing the through 
cars to pass through the car house for inspection or minor repairs 
if desired and relieving the main line of all special work. It may 
also be used as a ^^Y" for turning cars which must operate single 
ended. Designs (G) and (J) have been termed '^ bottle" en- 
trances involving the special work within the car house because 
of building conditions. (H) may be used often in interurban 
service where land is cheap and the car house may be placed at 
some distance from the main track. Case (I) involves the use 
of the third track in the street and therefore is limited to use 
with wide streets only. 

The special work required for any of the above entrances 
should be of girder rail with manganese hardened centers re- 
gardless of the type of rail used in the street and car house. 
This is especially true in cases in which the regular street traffic 
must pass over the switches and frogs as well as the cars entering 
the car house. 

Transfer Table. — The use of a transfer table in the car house 
often does away with much of the special work. This transfer 
table consists of a large truck operating upon a pair of depressed 
rails laid across the car house with its upper surface flush with 
the floor and bearing sections of rail matching those of storage 
house and outgoing tracks. A car may be run on this table in 
either direction, be transported transversely of the car house and 
run off on another track. The table may be operated by hand in 
small installations, but is ordinarily driven by an electric motor. 
A typical installation may be seen in Fig. 164. Although the 
transfer table may be found in many city car houses, it is seri- 
ously objected to by many because of the time required to shift 



CAR HOUSE DESIGN 



341 



cars, especially in case of fire, and the space taken up thereby, 
which might otherwise be available for storage. To obviate these 
objections the ''flush" transfer table is used to some extent, the 
cars being run up to the table on a slight gradient, the table 
trucks operating on a transverse track flush with the floor. 

Building Design. — With the above questions determined, the 
design of a suitable building for a car house is a relatively simple 
matter. The two factors to be kept constantly in mind are ease 
of handling and repairing cars and fire protection. 




Fig. 164. — Car house provided with transfer table. 



Fire Protection. — Car houses are recognized to be consider- 
able of a fire risk and many serious fires have consumed many 
thousand dollars' worth of rolling stock in a surprisingly short 
time, the entire duration of several such fires being barely 
more than 30 minutes. In many instances where there is a 
spacious yard room outside, the house rails are sloped toward the 
entrance so that the cars will coast out of the barn if brakes 
are released. In other cases many cars have been saved in case 
of fire by throwing the controller handle to the first notch and 
allowing them to run out without attendance. 

Not more than three tracks should be enclosed without a fire- 
proof partition and a single fire-proof section should not contain 
more than $200,000 worth of rolling stock as stipulated by the 



342 



ELECTRIC RAILWAY ENGINEERING 



Fire Underwriters. The best design is either brick walls with 
heavy mill type roof construction of fire-proofed timber or rein- 
forced concrete throughout. For the latter construction see Fig. 
164. Steel truss roof construction has proved very dangerous 
in cases of fire as the roof falls in very quickly, thus cutting off 
all possibility of getting out the remaining cars. Curtain walls 
of cement plaster on wire lath are often installed in long houses, 
separating the storage space into several fire-proof compartments. 
The front of the house and these curtain walls are provided with 
steel rolling doors. Opinion is divided regarding the advantages 
of timber roof trusses over posts for roof supports. The latter 
of course obstruct the working area somewhat, but are often used 
to advantage for lighting outlets, sprinklers and the convenient 




Fig. 165. — Typical car house elevation. 



support for fire fighting equipment. Automatic sprinkler systems 
are now being rapidly installed on ceilings and in aisles between 
cars for additional and prompt fire protection. These are sup- 
plied with sufficient head of water either from the city high pres- 
sure system or from a tank especially installed upon the premises. 
The appearance and relative dimensions of a typical car house 
elevation may be noted in Fig. 165. 

Pit Construction. — For convenience in inspection and repair, 
from 30 to 50 per cent, of the tracks in the car house are pit tracks, 
i.e., the floor between the rails is depressed several feet and 
cemented as shown in Fig. 165 in order that the under portion 
of the car may be accessible. It has also been found convenient 
to depress a portion of the floor between adjacent tracks by 1 
or 2 ft. for convenience in packing journal boxes, etc. 



CAR HOUSE DESIGN 



343 



Heating. — Car houses are heated principally by either steam 
or hot water, coiled pipes being located in pits and upon the 
lower portion of all walls. The boiler room, if not in a separate 
building, must be carefully protected by fire-proof walls. The 
heating of car houses is at best an unsatisfactory problem, 
especially in cases where the end doors must be continually open 
for the operation of cars. 

Floors. — The floors in small storage car houses are sometimes 
of gravel fill. This is not to be approved, however, on account 
of the impossibility of keeping such a floor in a sanitary condition. 
Heav}' timber flooring is probably most often found, but it should 




Fig. 166. — ^Example of good pit lighting. 



be avoided if the expense of concrete with cement finish can be 
seriously considered. Often the latter can be constructed with 
cinders from the power station without great expense and will 
prove the most satisfactory of all car house floors. Since sub- 
stantial piers must be laid for the track in whichever form it may 
take, the floor is generally supported therefrom. 

Lighting. — Incandescent lighting by means of five light series 
groups of lamps connected between trolley and ground is often 
used in smaller installations, but a low voltage ungrounded supply 
is much preferable. Lights spaced every car length in aisles 
are usually sufficient for general illumination if generous provision 



344 



ELECTRIC RAILWAY ENGINEERING 



be made for pit lighting and outlets for portable lamps. Pit 
lighting particularly should be in conduit as illustrated in Fig. 
166. General illumination for very large areas and for storage 
yards may be furnished by means of arc or large incandescent 
lamps, but these are not popular for car house installation. 

Offices and Employees' Quarters. — The arrangement of 
offices, employees' quarters and storage for raw materials and 




Man Hole 
m Ave. &. lUth St, 



Fig. 167. — Typical car house plan. 



tools is dependent upon local requirements and will not be dis- 
cussed in detail. The portion of the building containing the 
offices and employees' quarters is often of two stories and, where 
within the city limits, is designed to present a good architectural 
appearance. Many companies fit up spacious apartments, for 
the use of employees, rather elaborately with recreation and 
reading rooms, sleeping quarters, baths, etc. Provision should at 
least be made, however, for making out reports and for com- 



CAR HOUSE DESIGN 345 

fortably spending spare time between '^ reliefs." An average 
plan may be seen in Fig. 167. 

Repair Shops. — It is necessary to decide at first what the 
policy of the company is to be with regard to car repair and re- 
construction. If a large interurban company is to make all re- 
pairs, reconstruct damaged cars and possibly build new cars, a 
very elaborate series of forge, wood working, machine and paint 
shops will be necessary. The majority of the smaller companies, 
however, make only minor repairs, often sending away wheels 
for replacement or re-turning rather than install the lathes and 
hydraulic presses necessary for this work. Whereas the dis- 
cussion of the former type of shop is beyond the scope of this 
treatise, especially as comparatively few of the roads are thus 
equipped, the following average list may be of value in planning 
the equipment for a small shop. The machines are listed ap- 
proximately in the order in which they would be added with 
increased demands upon the repair shops. 

1 Screw cutting lathe, 14 in. swing. 

1 Vertical drill press, 24 in. 

1 Tool grinding wheel. 

4 Armature stands for rewinding armatures. 

2 Forges. 

1 Automatic power hack saw. 

1 Oven for baking insulation. 

1 Commutator slotting device. 

1 Wheel turning lathe. 

1 Hydraulic wheel press. 

Whereas the small repair shop as well as the paint shop often 
occupy sections of the main car house, the large shops are housed 
in separate but adjacent buildings. Such an arrangement, 
showing typical floor plan details, will be found in Fig. 167. 



CHAPTER XXVI 
ELECTRIC LOCOMOTIVES 

With the recent rapid advance in electric traction there has 
come the successful design, construction, and operation of several 
types of electric locomotives. While the Baltimore and Ohio 
Railroad had previously operated electric locomotives in its 
tunnels for several years, the great impetus in electric locomotive 
development came in 1903 as a result of the requirement that 
the tunnels entering New York City be electrified. This was 
done largely as a safety precaution soon after a serious wreck in 
one of these tunnels due to the inability to read signals on ac- 
count of the smoke inclosed in the tunnel. Likewise with the 
Cascade Tunnel of the Great Northern Railroad in Washington, 
experience with a train which parted in attempting to mount the 
severe grade of the tunnel with two steam locomotives, resulting 
in a delay of the train in the tunnel and the consequent over- 
coming by poisonous gases and smoke of the train crew and 
many passengers, led to the recent equipment of this section of 
the road with electric locomotives. 

Advantages of Locomotives over Motor Cars. — With the 
multiple unit control of motor cars, which has been previously 
described, developed to such an extent that long heavy trains 
of both motor cars and trailers are being operated successfully 
in elevated, subway and interurban service, offering a very flexible 
distribution of motive power and weight on driving wheels 
throughout the train, it might be expected that this method of 
propulsion would be applied to the heavier electrification of 
steam roads. As the traffic demands and the number of cars 
increased, motor and trail cars could then be added in the proper 
proportion so as to leave little excess capacity to operate at low 
efficiency as must often be the case with but one or two capacities 
of locomotives used for trains of widely varying weights and 
requirements. 

In spite of these advantages of the motor car, the locomotive 
is still found to be necessary in heavy trunk line service. Its 

346 



ELECTRIC LOCOMOTIVES 347 

advantages listed below can be made to overcome those of the 
motor car by dividing the service into three or four classes such 
as switching, suburban, express, passenger and heavy freight 
and designing different locomotives, if necessary, for two or more 
of these types of service, thus keeping the locomotive loaded 
approximately to its rated capacity. The advantages of the 
locomotive in heavy service may be listed as follows: 

1. It eliminates necessity of re-equipping present cars as motor 
cars. 

2. It eliminates necessity of wiring some of the present cars 
with train cables for use as electric trailers. 

3. Ease in making up trains regardless of whether they have 
been electrically equipped or not — i.e., the electric locomotive 
makes use of present cars without change therein. 

4. Not necessary to make up trains in certain order with proper 
number and location of motor cars therein. 

5. Ease in reaching parts in locomotive for repair. 

6. Make up of train not affected by failure of electrical equip- 
ment. Locomotive only, and not several cars of train, must be 
switched in case of electrical breakdown. 

7. First cost of motive power equipment is lower. 

8. Maintenance expenses of motive power are lower. 

At present the motor car train seems to offer the most ad- 
vantages for accommodation passenger and suburban service, 
while the locomotive seems best adapted for the long haul 
passenger and freight service. 

Granted that an electric locomotive is needed if trunk line 
service is to be electrified, a study of the various types of electric 
locomotives which are in use at the present time is of interest. 
With the many years of experimenting and practical experience 
with steam locomotives which have led to a most satisfactory 
design for the various types of service, advantage was taken of 
present steam locomotive design and the electrical equipment 
added with as little change as possible. To this end the manu- 
facturers of steam locomotives and electrical machinery have 
cooperated to a marked degree in developing the new product. 

Locomotive Ratings. — The standardization rules of the 
American Institute of Electrical Engineers require that locomo- 
tives shall be rated in terms of the adhesive weight, nominal 1 
hour tractive effort, continuous tractive effort and corresponding 
speeds. The nominal and continuous tractive efforts are those 



348 



ELECTRIC RAILWAY ENGINEERING 



corresponding to the nominal and continuous outputs of the 
motors. (See Chap. XXII.) The rated speed is the speed ex- 
pressed in miles per hour when the motors are operating at 
their full voltage, continuous rating. The tractive effort ex- 
erted at 25 per cent, coefficient of adhesion is also often given. 
Locomotive Data. — The following tables, made up of data col- 
lected from many sources, give concisely some of the more im- 
portant details of modern American electric locomotives: 



Table XXXIX. — Date on General Electric Co. Locomotives 



Road 



N. Y. C. 

&H. R. 

R. R. 



Butte, Ana 
conda & 
Pacific Ry 



Oregon 

Electric 

Ry. 



Great 

Northern 

Ry. 



Electric system 

Service 

First placed in service 

Contact line voltage 

No. of motors 

Mechanical transmission 

Gear ratio 

Control 

Motor ventilation 

Underframe 

Body construction 

Wheel arrangement 

Drive wheel diameter 

Rigid wheel base 

Total wheel base 

Length inside of knuckles 

Total weight 

Weight per driving axle 

Adhesive weight 

T.E. (1 hour) 

T.E. (continuous) 

Speed in m.p.h. (1 hour rating) . . . . 
Speed in m.p.h. (continuous rating) 

1 Hour hp 

Continuous hp 

1 Hour hp. per ton 

1 Hour T. E. per ton 



D. c. 

Terminal 

passenger 

1908 

600 

4 

Direct 

G earless 

Type M 
Natural 
Cast steel 

Steel 
4-8-4 
44 in. 
13 ft. in 
36 ft. in 
41 ft. in, 
230,000 
36,000 
144,000 
20,. 500 
6,700 
40 
57 
2,200 
1,000 
19.1 
178 



D. c. 

Main line 

freight 

1913 

2400 

4 

Gears 

87 

18 

Type M 

Forced 

12 in. 

channels 

Steel 
0-4-4-0 
44 in. 
8 ft. 8 in. 
26 ft. in. 
37 ft. 4 in. 
160,000 
40,000 
160,000 
30,000 
25,000 
15 
16.2 
1,200 
1,080 
15 
375 



D. c. 

Interurban 

freight 

1912 

600/1200 

4 

Gears 

64 

17 

Type M 

Natural 

10 in. 
channels 

Steel 
0-4-4-0 
37 in. 
7 ft. 2 in. 
26 ft. 8 in. 
37 ft. 4 in. 
100,000 
25,000 
100,000 
13,300 
8,000 
11.3 



40C 



265 



3-phase a. c. 

Main line 

freight 

1909 

6600 

4 
Gears 
81 
19 
Type M 
Forced 
Structural 
steel shapes 
Steel 
0-4-4-0 
60 in. 
11 ft. in. 
31 ft. 9 in. 
44 ft. 2 in. 
230,000 
56,000 
230,000 
39,800 
25,000 
15.1 
15.3 
1,600 
1,000 
13.9 
346 



Modern Electric Locomotives. — The New York Central loco- 
motive, Fig. 168, of the direct current type, a plan view of whose 
motor is shown in Fig. 169, marked a radical departure in rail- 
way motor design. As will be noted from the figure, the motor 
is bipolar, the magnetic circuit involving a portion of the truck 
frame with internally projecting laminated iron poles with vertical 
faces, between which the armature, mounted directly on the 



ELECTRIC LOCOMOTIVES 



349 



Table XL. — Data on Westinghousb Locomotives 



Road 



N. Y., N. H. 
& H. Ry. 



N. Y., N. H. 
& H. Ry. 



Pennsylvania 
R. R. 



Norfolk & 
Western R. R. 



Electric system 

Service 

First placed in service 

Contact line voltage 

Number of motors 

Mechanical transmission 

Gear ratio 

Control 

Motor ventilation 

Underf rame 

Cab body construction 

Wheel arrangement 

Drive wheel diameter 

Rigid wheel base 

Total wheel base 

Length inside of knuckles 

Total weight 

Weight per driving axle 

Adhesive weight 

T.E. (1 hour rating) 

T.E. (continuous) 

Speed in m.p.h. (1 hour rating) . . . 

Speed in m.p.h. (continuous rating) 
1 Hour hp 

Cont. hp . 

1 Hour hp. per ton 

1 Hour T.E. per ton 



Terminal 
passenger 
1908 



11,000 
4 
Direct 

(mounted on 
quill) 

Gearless 

A. c.-D. c. 
Master cont 

Forced 

Steel chan- 
nels and 
girder con- 
struction 

Steel 

2-4-4-2 

62 in. 

8 ft. in. 

30 ft. 10 in. 

36 ft. 4 in. 

204,000 

38,500 

154,000 

8,900 

5,900 

40.5 

51.5 
960 

800 

9.3 

87.5 



A. c.-D. c. 

Main line 
term, freight 
1909 

11,000 
4 
Geared to 
quill 

2.32 
A. c.-D. c. 

Master cont. 

Forced 

Structural 
steel 



Steel 

2-4-4-2 

63 in. 

7 ft. in. 

38 ft. 6 in. 

48 ft. in. 

280,000 

48,000 

192,000 

15,000 

12,000 

30.3 

35 
1,260 

1,120 

9.0 

111.5 



D. c. 



Terminal 
passenger 
1910 



600 

2 

Connecting 

rods and 

jack shaft 

Gearless. . . . 

H.B. 



Natural . . . 
Cast steel. 



Steel 

2-4-4-2 

72 in. 

7 ft. 2 in. 

55 ft. 11 in. 

64 ft. 11 in. 

314,000 

50,000 

200,000 

42,000 

(30 minutes) 

9,000 

36 
(30 minutes) 

67 

4,000 

(30 minutes) 

1,600 

25.5 

(30 minutes) 

267 
(30 minutes) 



Split phase 

A. c. 
Main line 
freight. 
1914 (buUd- 

ing). 

11,000 
4 
Gears and 
side rods. 



Master cont, 

3-phase. 
Forced. 



2-4-4-2 

63 in. 

11 ft. in. 

43 ft. in. 

52 ft. in. 

260,000 

55,000 

220,000 

43,700 

20,000 

34,300 

14 

/28.3 Two 
\ 14.2 speeds 
1,640 

1,500 at 28.3 
1,300 at 14.2 
12.6 

337 



truck axle, might vibrate in a vertical direction with the irregu- 
larities in the track. This design, of course, greatly increased the 
capacity possible in the limited space on the truck, eliminated 
many of the disadvantages of the small air gap and gave con- 
siderable flexibility to the relative movement of armature and 
field. It also lowered the center of gravity of the locomotive 
below that of its steam railroad competitor and increased the 



350 



ELECTRIC RAILWAY ENGINEERINO 



dead load per axle, both of which changes have been considered 
as disadvantageous by some engineers. 

The locomotives of the New York, New Haven & Hartford 
Railroad, Fig. 170, which were developed soon after the above 




New York Central locomotive. 



for operation upon the 11,000 volt single-phase system of the 
above company not only, but also upon the 600 volt direct 
current system of the New York Central Railroad entering New 
York City still retained the motors concentric with the truck 




an view, New York Central motor 



axles and between the driving wheels as will be seen from Fig. 
171, but reduced the dead weight upon the axles by supporting 
the armature upon a quill, concentric with, but surrounding the 
driving axle with a space of % in. between axle and inner cir- 



ELECTRIC LOCOMOTIVES 



351 




Fig. 170.— N. Y., N. H. & H. locomotive. 




Fig. 171.— ]\Iotor and drivers of N. Y., N. H. & H. locomotive. 



352 



ELECTRIC RAILWAY ENGINEERING 




Fig. 172. — Armature and driving pins, N. Y., N. H. & H. locomotive. 




Fig. 173. — Pennsylvania R. R. locomotive. 



ELECTRIC LOCOMOTIVES 



353 



cumference of quill. The torque was transmitted from armature 
to drivers by means of seven driving pins, spring borne in recesses 
in the driving wheels as shown in Fig. 172. This allowed the axle 
considerable motion independent of the armature not only, but 
permitted the motor field and frame to be rigidly supported upon 
the truck. In order to improve their riding qualities the pony 
wheels were added to each of these locomotives in 1908. 
The Pennsylvania locomotives, Fig. 173, were built for service 




1000 
2000 



1500 



2500 
5000 



3000 



2000 
Motor Amperes 
4000 
Locomotive Amperes 

Fig. 174. — Characteristic cun^es, Pennsylvania locomotive. 



through the New York tunnels and yards of the Pennsjdvania 
Railroad. The locomotives are of the articulated tj^pe, two 
similar sections being set back to back, and articulated together 
with a heavy hinge which permits horizontal movements only. 
Each section of the locomotive contains a single large motor 
which is mounted in the cab and has a maximum rating of 2,000 
hp. at 600 volts. At starting, the current input to the locomo- 
tives sometimes reaches 7000 amp. The motors are of the field 
control type and have four efficient running speeds. 

23 



354 



ELECTRIC RAILWAY ENGINEERING 




Fig. 175. — Direct current freight locomotive. General Electric Co. 



40 80 



o 25"^ 50 



20 .S 40 

1 
u 
H 

15 ^ 30 



10 20 



5 10 







\ 
















\ 


















\ 










/ 


100 




\ 


Motor F 


faciency ( 


m 1200 Vc 


Its . 


/ 


x^ 


\ 






:^ 






/ 




>^e^ 


^ 


r 




GO 
40 
20 









/ 


/ ^ 






















^ 













'0 100 200 300 400 500 600 700 

Amperes per Locomotive 

Fig. 176. — Characteristic curves, Butte, Anaconda & Pacific k)comotive. 



ELECTRIC LOCOMOTIVES 



355 



1. Series connection with full field. 

2. Series connection with normal field. 

3. Parallel connection with full field. 

4. Parallel connection with normal field. 




Fig. 177. — Interurban locomotive. General Electric Co. 

The characteristic curves of this locomotive are given in 
Fig. 174. 

The Butte, Anaconda & Pacific locomotive, Fig. 175, whose 
characteristic curves are given in Fig. 176 is a recently developed 
type of freight locomotive. It is built for operation in connection 
with a 2400 volt direct current trolley line, and is equipped with 




Fig. 178. — Outline diagram of C. M. & P. S. Ry. locomotive. 



four commutating pole motors. The motors are wound for 1200 
volts and insulated for 2400 volts, and are operated with two 
motors permanently connected in series. (For detailed data, 
see Table XXXIX.) 

The locomotive illustrated in Fig. 177 is a typical interurban 
freight locomotive. (For detailed data, see Table XXXIX.) 



356 ELECTRIC RAILWAY ENGINEERING 

The direct current locomotives recently ordered of the General 
Electric Company by the Chicago, Milwaukee & Puget Sound Ry. 
for its mountain grade electrification, in weight and rating 
surpass any locomotive either steam or electric which is now in 
service. A skeleton diagram of this proposed locomotive is shown 
in Fig. 178. The following is a summary of the principal dimen- 
sions and weights. 

Length inside of knuckles 112 ft. 8 in. 

Total wheel base 103 ft. 4 in. 

Wheel base for each unit 46 ft. 7 in. 

Total weight 260 tons. 

Adhesive weight 400,000 lb. 

Weight per driving axle 50,000 lb. 

Diameter of drivers 52 in. 

Continuous horse power 3,000 

1 Hour horse power 3,440 

It is designed for operation in connection with a 3000 volt 
overhead contact line, and will be equipped with eight G. E. 
No. 253-A type motors. These motors are wound for 1500 
volts and insulated for 3000 volts. The eight motors will be 
divided into four groups, the two motors forming one group being 
permanently connected in series. The motors and control system 
will be arranged to permit regenerative braking on down grades. 
The motor equipment will enable a freight locomotive to haul a 
2500 ton train up a 1 per cent, grade at a speed of 16 m.p.h. 
For passenger service a gear ratio such that a locomotive can 
haul an 800 ton train at a speed of 60 m.p.h. on level track will 
be used. On account of the long flexible wheel base, well dis- 
tributed wheel loads, and guiding trucks these locomotives should 
possess excellent riding qualities. 

Split -phase Locomotive — This type of locomotive is equipped 
with polyphase motors which receive their energy supply through 
a phase converter from a single-phase contact line. Fig. 179 
illustrates the phase converter which has been developed by the 
Westinghouse Electric & Manufacturing Company. Essentially 
it consists of a high speed single-phase induction motor on the 
stator of which is placed a second winding in electrical space 
quadrature with the main winding. This second winding has 87 
per cent, as many turns as the main winding. One end of this 
winding is connected to the midpoint of the secondary winding 
of the locomotive transformer. The outer secondary terminals 



ELECTRIC LOCOMOTIVES 



357 



and the remaining terminal of the second stator winding form the 
three-phase terminals to which the motors are connected. This 
connection of windings is similar to the well-known Scott two- 
phase to three-phase system of transformer connections, the 
quadrature voltage required being furnished by the second wind- 
ing of the phase converter. The small motor which is direct 
connected to the phase converter is a series single-phase motor 
and is used in starting the phase converter. 




Fig. 179. — Phase converter for Westinghouse split phase locomotive. 

Mercury Vapor Rectifier Locomotive. — In an effort to combine 
the good qualities of the single-phase alternating current dis- 
tribution system and the direct current series motor, much time 
and money have been expended in the development of a large 
capacity mercury vapor rectifier of such design that it could be 
mounted on a locomotive or motor car and could be depended 
upon to withstand the severe conditions of railway service. A 
locomotive equipped by the Westinghouse Electric & Manu- 
facturing Company with such a rectifier has recently completed 
successfully a 20,000 mile service test. The electrical equip- 
ment consists of a transformer with adjustable ratio, for lowering 
the trolley voltage to a value suitable for the rectifier; two 
rectifier tubes, one for service and one for reserve; four 250 hp. 
600-volt motors and the necessary control apparatus. The 
motors are of a standard direct current design but no trouble was 
experienced in operating them on the pulsating current supplied 
by the rectifier. A simplified diagram of the electric circuits is 
shown in Fig. 180.^ 

1 Electric Railway Journal^ Dec. 19, 1914, 



358 



ELECTRIC RAILWAY ENGINEERING 



The rectifier consists of a light, hned steel cylinder, approxi- 
mately 20 in. in diameter and 30 in. in height. The voltage drop 
in the rectifier is about 25 volts for all values of current so that 
the efficiency at 1200 volts is very high. This type of a.c.-d.c. 
equipment has high power factor, high efficiency, good motor 
characteristics, flexibility, and is light in weight. Its probable 
disadvantages are complication, high first cost of motive power 
unit, and high maintenance charges. 




Motors 

Fig. 180. — Simplified diagram of rectifier locomotive connections. 

Design Requirements. — The electric locomotive is not an 
absolutely interchangeable machine, but like the motor car, it 
gives the most satisfactory results when designed for the par- 
ticular service in which it is to be used. Briefly stated, some of 
the more important requirements for a given service are: 

1. Ample motor and mechanical transmission capacity. 

2. High factor of safety of mechanical parts. 

3. Economy in operation. 

4. Safety and reliability in operation. 

5. Accessibility for inspection and repairs. 

6. An adequate control system. 

7. The locomotive must not be destructive to the track struc- 
tures. 

Some of the factors which are affected by the preceding 
requirements will now be considered. 

Motor Mountings and Transmissions. — In the early loco- 
motives it was believed to be necessary to mount the motors on 
the driving axles between drivers as in the case of motor cars 
with consequent limitation in capacity of motors on account of 
gauge of track and short wheel base. The change of track gauge 



ELECTRIC LOCOMOTIVES 



359 



was of course practically impossible with the present installa- 
tion of standard gauge roads in the countrj^ and an increase in 
the length of wheel base introduced difficulties in rounding 
curves. In fact, any limitation upon the flexibility of the truck 
and the free and independent vertical and transverse movement 
of individual axles with irregularities in the track tends to move 
the entire mass of the locomotive, thus introducing bad riding 
quaUties and vibrations which become dangerous at high speeds. 
An attempt was first made, therefore, to vary the design of the 




Fig. 181. — Gearless motor 
mountings. 



Fig. 182. — Geared motor 
mountings. 



large interurban motors to gain greater capacity upon the 
limited size of trucks and later to remove the motor from the truck 
axles, as will be shown hereinafter. 

After some few years of experience with the operation of the 
earher locomotives and a careful study of their characteristics as 
compared with steam locomotives, the principal problem in 
design seemed to be resolved to that of the transmission be- 
tween motor axle and driving wheels. Messrs. Storer and 
Eaton in a recent paper before the American Institute of Electrical 



360 



ELECTRIC RAILWAY ENGINEERING 



Engineers^ have presented this problem in a very concise form 
and because of its importance in electric locomotive design and 
as designing engineers in both this country and abroad are 
at variance regarding the best method of transmission to adopt, 
a statement of the various types in use, together with illustra- 
tions of each have been taken from the above paper and are 
herein included. 

(a) " Gearless motor with armature pressed onto driving axle, 'New 
York Central,' Fig. 181, a. 

(6) ''Gearless motor with armature carried on a quill surrounding 
axle, and driving the wheels through flexible connections, 'New Haven 
Passenger,' Fig. 181, b. 

(c) ''Geared motor with bearings directly on axle and with nose 




Fig. 183. — Motor mounting on Pennsylvania locomotive. 

supported on spring-borne parts of locomotive, 'St. Clair Tunnel,' Fig. 
182, c. 

(d) "Geared motor with bearings on a quill surrounding axle, and (1) 
nose supported on spring-borne parts of machine, New Haven Car, 
Fig. 182, d, and (2) motor rigidly bolted to spring-borne parts of machines, 
the quill having sufficient clearance for axle movements, ' Four motor 
New Haven Freight,' Fig. 182, d\ 

(e) "Motor mounted rigidly on spring-borne parts, armature rotating 
at same rate as drivers, power transmitted to drivers through cranks, 
connecting rods and counter-shaft on level with driver axles. 'Penn- 
sylvania,' Fig. 183. 

(/) " Motor mounting and transmission as in (e) but motor fitted with 
double bearings one part for centering motor crank axle and the other for 

^ "The Design of the Electric Locomotive," by N. W. Storer and G. M. 
Eaton, A. 1. E. E., Vol. XXIX. 



ELECTRIC LOCOMOTIVES 



361 



centering the armature quill which surrounds and is flexibly connected 
to the motor crank axle. 'Two motor New Haven Freight/ Fig. 184,/. 
{g) "Motors mounted on spring-borne parts, armature rotating at 
same rate as drivers, power transmitted to drivers through off-set con- 
necting rods and side rods. 'Latest Simplon Locomotives,' Fig. 184, g. 




Fig. 184. — N. Y., N. H. & H. and foreign motor mountings. 

{h) ''Motors mounted on spring-borne parts, armature rotating at 
same rate on drivers, power transmitted to drivers through Scotch 
yokes and side rods. 'Valtellina Locomotives,' Fig. 184, h. 

(i) "Motors mounted rigidly on spring-borne parts, power trans- 
mitted through gears to counter-shaft, thence to drivers through Scotch 
yokes and side rods. Fig. 185." 




* Fig. 185. — Mounting with both gears and connecting rods. 

It will be seen from the preceding that the locomotives of the 
Pennsylvania Railroad mark a rather radical departure from the 
designs previously described, having their motors above the 
trucks in the cab and returning to the connecting rods of the steam 
locomotives for transmission to the drivers. This design raises 
the center of gravity and permits practically unlimited motor 
capacity in a single unit as its dimensions may be increased 



362 ELECTRIC RAILWAY ENGINEERING 

longitudinally at will and transversely by overhanging the 
driving wheels. 

In general it may be said that gears offer a very satisfactory 
transmission for a low speed locomotive, such as is used in freight 
and switching service, but they do not seem to be able to stand 
up under the heavy impact strains which accompany high speed 
operation. On the other hand, slow speed gearless motors are 
excessively large and heavy, because the peripheral speed of the 
armature is below the most economical value; they are therefore 
best adapted for high speed operation. 

Locomotive Weights. — The locomotive weights used in various 
classes of electric railway service have been indicated in Chap. 
XI. The weights and dimensions of interurban locomotives are 
usually limited by roadway conditions, such as strength of 
bridges, weight of rail, spacing of ties, overhead and side clear- 
ances, and by the maximum peak loads allowed on the power dis- 
tribution system and power plant. It is feasible to build loco- 
motives for heavy traction service in very large sizes, but it is 
not necessary to do so, as the multiple unit control system permits 
any desired number of locomotives to be operated as a single 
unit. Besides, small units may be more readily shopped, and 
while in the shop do not tie up as much capital as do the larger 
units. 

A study of the tables on pages 348 and 349 indicates that the 
weight per driving axle varies considerably in the different de- 
signs. Axle loads up to 72,000 lb. have been used in steam 
locomotive practice, but such loads make roadway maintenance 
very costly. In well-designed heavy electric locomotives the 
driving axle loads usually range between 35,000 and 50,000 lb. 
The weight on drivers must be sufficient that the adhesion of 
the locomotive will permit the motors to be worked up to their 
overload rating, yet must not be so great that the motors will 
be dangerously overloaded before the drivers slip. 

Drive Wheels. — Drive wheel diameters vary from 33 in. to 
72 in. Small drive wheels cannot be used with gearless motors 
because they limit the diameter and therefore the capacity of 
the motor armatures. Other considerations which tend to fix 
the minimum size of the drive wheels have been given in Chap. 
XI. Considerations of motor, transmission, and frame design 
fix the maximum limits of drive wheel diameter. 

Drive wheels for large locomotives are usually constructed with 



ELECTRIC LOCOMOTIVES 363 

a steel tire shrunk on a cast steel core. Either solid rolled steel 
or cast iron wheels with chilled treads are used on the smaller 
locomotives. The treads are usually made to conform to the 
specifications of either the Master Car Builders' Association or the 
American Electric Railway Association. 

Trucks. — The length of the rigid wheel base of a truck is limited 
by the sharpest track curve which must be negotiated by the 
locomotive. Many different truck designs are in use. A modi- 
fied form of the M. C. B. type is much used for small locomotives. 
Trucks for heavy locomotives are usually articulated or hinged 
in order to prevent ''rearing up" of the ends of the trucks when 
the motors are exerting large tractive efforts. Since the trucks 
transmit the entire tractive effort of the locomotive, they must 
be heavy and strong. As has already been intimated, the de- 
sign of the main trucks is usually dependent to a greater or less 
extent on the type of motor mounting used. For speeds above 
40 m.p.h., or for operation over track which has many sharp 
curves, pony or guiding trucks are usually necessary. These 
trucks must carry sufficient weight in order that they may 
properly perform their functions. 

Cab Underframing. — The cab underframing is a vital part of 
the locomotive. In most cases it transmits the tractive force 
developed by the motors to the drawbar and supports the cab 
and a great part of the locomotive equipment. It must be 
strong enough to withstand enormous bumping strains and shocks. 
For heavy service, the frames are often designed to withstand 
bumping forces equivalent to a static load of 500,000 lb. In 
general, the underframing is similar to that used in steam locomo- 
tive tender construction. Heavy channel or I-beams are used 
for the longitudinal members or sills. These are riveted to heavy 
cast steel end sills. The body bolsters and steel sheet floor 
are also riveted to the sills, thus making an exceedingly strong 
platform construction. Since standard structural shapes may 
be used, this form of construction is very economical. Some 
engineers advocate the use of frames built up of plate metal as they 
are a little more flexible in the vertical plane and permit a little 
better equalization of the load on the drive wheels. Such frames 
are much used abroad but have not been used to any considerable 
extent in this country. 

Cabs. — Cabs may be either of the box type. Fig. 170, or steeple 
type. Fig. 177. For heavy road locomotives the box type cab 



364 ELECTRIC RAILWAY ENGINEERING 

is commonly used. Control positions are located at each end. 
The air compressor, blower for motor, ventilating system, switch 
groups, and other auxiliary apparatus are conveniently located 
on the cab floor. 

Cabs are built either of wood or steel. The latter is preferable, 
but is more expensive. For service in cold climates steel cabs 
should be lined with wood or some heat insulating composition, 
and both steel and wood cabs should be provided with heaters. 
Locomotives designed for passenger service sometimes carry an 
oil fired steam boiler in the cab for the purpose of heating the 
cars. 

Interurban and switching locomotives are often equipped with 
steeple type cabs. In these cabs the auxiliary apparatus is 
placed under the steel hoods at either end. On switcher locomo- 
tives only one control position need be installed. 

In general, the cab should be well lighted, have convenient 
doors and lookout windows, and be so constructed that the cab 
itself can be removed with a minimum derangement of apparatus. 

Riding Qualities. — Not only must a locomotive be able to 
start a train and have sufficient power to haul it at the required 
speed, but it must perform the above duties with maximum 
safety and minimum destruction of roadway. Track hammer- 
ing and ''nosing'' of the locomotive are the principal causes of 
track destruction and resulting wrecks. Heavy dead weights 
(non-spring-borne weights) and unbalanced rotating parts both 
cause hammer blows to be delivered to the rail head. The ex- 
cessive vibration which occurs when an improperly designed loco- 
motive is operated at high speed is also very destructive to road- 
way. Nosing or the swinging back and forth of a locomotive 
in a direction transverse to the track, tends to loosen the spikes 
and overturn the rails, either by the direct pressure of the wheel 
flange against the rail head or by impact blows. While it is im- 
possible to eliminate nosing entirely, serious results may be 
prevented by the following means: 

1. The use of pilot trucks. Pilot trucks tend to guide the 
locomotive around curves and prevent transverse movements 
of the ends of the locomotive; the lateral thrust of the wheels 
against the rails acting as a guiding force which has for its lever 
arm the horizontal distance from the center of gravity of the 
locomotive to the effective turning center of the pilot truck. 

2. Restraining the transverse movements by means of springs. 



ELECTRIC LOCOMOTIVES 365 

Oscillations around the vertical center of gravity axis are thus 
dampened and impact blows on the side of the rail heads 
prevented. 

3. Permitting a certain amount of vertical and transverse move- 
ments of the individual axles. Movements imparted to the in- 
dividual axles by uneven track or small obstacles will be taken 
up by the axles themselves and not imparted to the entire mass 
of the locomotive. 

4. Massing the hulk of the weight as near the center of gravity of 
the locomotive as possible. When this is done only a small guiding 
force will be necessary to keep the locomotive body in its proper 
position relative to the track and transverse oscillations are 
easier to dampen out. The excessive nosing often noticed when 
single truck cars and switcher locomotives are operated at fairly 
high speeds is largely due to the large amount of overhanging 
weight. 

5. Keeping the center of gravity high. The distance from the 
point of restraint to the center of gravity is thus increased, there- 
by decreasing the movement which tends to cause oscillations 
about the center of gravity. 

The first passenger locomotives built for both the N. Y. C. & 
H. R. R. R. and the N. Y.,N. H. & H. R. R. gave much trouble 
on account of their serious nosing. The riding qualities of both 
types were greatly improved by the use of pilot trucks. Loco- 
motive builders, profiting by the experience gained in the opera- 
tion of these locomotives, are now building locomotives which 
have very excellent riding qualities. 

Costs. — Since most of the locomotives now in service were at 
first more or less experimental and had large development charges 
included in their first costs, authentic information regarding loco- 
motive costs is difficult to obtain. Cost data that have been 
published from time to time indicate that the first costs range 
from 12 to 26 cts. per pound. Locomotive maintenance and 
repair costs largely depend on the nature of the service in which 
the locomotive is operated. A study of Interstate Commerce 
Commission reports and other published data indicates that 
these costs range from 3 to 12 cts. per locomotive mile, with an 
average value of about 5 cts. 

Although some arguments in favor of the electric locomotive 
as compared with its steam rival will be considered in a later 
chapter, it may be said in the conclusion of this discussion that 



366 ' ELECTRIC RAILWAY ENGINEERING 

the electric locomotive has accomplished thus far all that has 
been required of it, i.e., to operate as satisfactorily as the steam 
locomotive under all conditions of service and eliminate the 
disadvantages coincident with smoke and dirt of the latter. It 
has also shown itself capable of accelerating more rapidly than its 
competitor, which particularly commends it where headway is 
short and stops are frequent. It can readily be designed for 
a draw bar pull far in excess of that of the largest steam loco- 
motives. It has therefore found a permanent place in the 
electrification of terminals. Its future now seems to be one of 
further adaptation and adoption, although its depreciation and 
maintenance in comparison with the steam locomotive can hardly 
be intelligently compared at present. 



PART IV 

TYPES OF SYSTEMS 



CHAPTER XXVII 

ALTERNATING CURRENT VS. DIRECT CURRENT 
TRACTION 

The problem to be discussed under the above caption is one 
that has received much attention during the past few years by 
steam and electric railroads officials, consulting engineers and 
electrical manufacturing companies. It has been the target of 
much discussion before technical societies and in the technical 
press, at times involving rather heated criticisms based upon 
both accurate engineering data and the enthusiastic prophecies 
of more or less prejudiced engineers. To sift out the salient 
factors in the case and outline the present status of the problem 
in a few words becomes, therefore, a difficult ta&k. 

Whereas the greater part of the discussion of this subject has 
been in connection with the electrification of steam roads, because 
of the prominence of the latter problem at the present time, 
before which the selection of a motive power for an interurban 
system immediately becomes dwarfed in magnitude, yet its con- 
sideration has purposely been made to precede that of ^'Electric 
Traction on Trunk Lines" because of its broader applicability 
to interurban systems, steam railroad electrification, and possibly 
J30 city traction systems under some peculiar local conditions. 

Electric Systems. — The systems which have sufficient ad- 
vantages and for which complete power station, distribution and 
rolling stock equipment have been sufficiently developed to 
warrant consideration in this problem are the following: 

1. Direct current system. 

2. Single-phase alternating current system. 

3. Three-phase alternating current system. 

4. Combined systems. 

The preceding systems of electrification classified either as to 
kind of motors or as to kind of contact line used are: 

1. Direct current. 

2. Single-phase alternating current. 

3. Three-phase alternating current. 
24 369 



370 ELECTRIC RAILWAY ENGINEERING 

Most of the component parts of the above systems have been 
described in previous chapters. However, for convenience in 
the study of this chapter a brief description of each system is 
here given. 

Direct Current System. — This system was the first one de- 
veloped. It is used on practically all city lines, most interurban 
lines, and on a large percentage of the trunk line electrifications 
in this country. The contact line voltages range from 500 to 
3000 volts. Electrical equipment manufacturers have ex- 
perimented with voltages up to 7000 with promising results, and 
it is quite probable that still higher voltages will be used in the 
near future. The contact line, which may be either an over- 
head trolley or a third rail, and its feeders receive energy from 
substations located along the line. The motor cars and loco- 
motives are equipped with direct current series motors. 

Single -phase System. — Either series or modified repulsion, 
commutator type, single-phase motors are used. Contact line 
voltages range from 3300 to 25,000 volts. The contact line 
receives energy from transformer substations located along the 
line. This system has been used only in interurban and trunk 
line service, the high contact line voltages being considered too 
dangerous for operation on city streets. 

Three-phase System. — The locomotives are equipped with 
three-phase induction motors. Two overhead contact lines 
are used, the track rails forming the third conductor of the 
three-phase circuit. Transformers on the locomotive are used 
to lower the contact line voltage to a value suitable for the 
motors where high contact line voltages are used, although for 
voltages up to 3000 the transformers are often dispensed with. 
The contact lines receive their energy supply from transformer 
substations as in the case of the single-phase system. While 
the great majority of railways now using electric motive power 
use either the direct current or the single-phase systems, three- 
phase locomotives with an aggregate rating of approximately 
300,000 hp. are in use at the present time, chiefly on the moun- 
tain grade railways of Italy. 

Combined Systems. — Several combined systems have been 
proposed. The most important of these are the split-phase and 
single-phase rectifier systems. In both of these systems a single- 
phase contact line is used so that the distribution system is 
identical with that of the single-phase system. 



ALTERNATING VS. DIRECT CURRENT TRACTION 371 

The locomotives in the spUt-phase system are equipped with 
three-phase motors and a phase converter for converting the 
single-phase energy received from the contact line to the three- 
phase energ}^ required by the motors. 

This system, which is a recent development, has been adopted 
by the Norfolk & Western Railway in its mountain grade 
electrification in West Virginia. 

An experimental locomotive of the single-phase rectifier type 
has already been discussed in Chap. XXVI. The system has 
not been installed by any railway and as yet is only in the de- 
velopment stage. It has many advantages and its success as a 
practical system wall depend altogether on whether or not 
a suitable rectifier can be developed. 

Comparison of Systems. — The various systems will now be 
compared upon as nearly the same basis as possible. The 
peculiarities of each system, which may result in advantages or 
disadvantages depending upon local conditions in each installa- 
tion, will be discussed in connection with the several determining 
and distinctive functions of the complete railway S3^stem. 

Power Station. — The power station is not materially different 
for the various systems for a long road, involving as it does three- 
phase generating equipment and step-up transformers, together 
with the control of three-phase high tension transmission lines. 
If those systems employing a single-phase contact line be operated 
with a single-phase generating station, which is the exception 
rather than the rule, the first cost and size of generating equip- 
ment are increased for a given output, but the switchboard and 
control are slightly simplified. 

Even when three-phase generating equipment is used, the 
generators for those systems employing alternating current 
motors must have* a higher aggregate rating than would be neces- 
sary for the systems employing direct current motors, the power 
output of the power plant being assumed the same for each sys- 
tem. This is because, with the systems employing alternating 
current motors, the generators must be operated at less than unity 
power factor. It must not be inferred, however, that greater 
prime mover capacity will be required. Murray of the New 
York, New Haven & Hartford Railroad claims^ the energy re- 
quired to handle a given weight of traffic is 22 per cent, more with 

^ Discussion before Canadian Society of Civil Engineers, Dec, 1913. 



372 ELECTRIC RAILWAY ENGINEERING 

direct current than with alternating current. The results of the 
exhaustive studies of the Swiss Railway Commission seem to 
confirm in a general way Murray's claim, although they do not 
check his figures. Taking into account this decrease in the 
amount of energy required and the lower power factor of the 
alternating current systems it will be seen that for a given weight 
of traffic carried, the capacity of the power station equipment is 
practically the same for all systems. 

Transmission Lines. — No material difference exists between 
the systems in regard to transmission, so long as three-phase 
transmission is adopted. The costs of these lines for all systems 
are therefore practically identical. In the comparatively few 
installations where single-phase transmission might be adopted, 
the design and construction of the line is simplified by the use of 
two wires in place of three, but for a given power transmitted 
and a fixed efficiency of transmission the cost of copper in the 
three-phase system is 25 per cent. less. This will usually more 
than balance the added installation and maintenance cost of the 
third wire. 

Substation. — In the design of the substation is found one of 
the most marked variations in the systems. As explained in 
a previous chapter, the direct current system requires the in- 
stallation of transformers, synchronous converters or motor 
generators and switchboards in the substation, whereas the alter- 
nating current systems call for the transformers and automatic 
control switches only. This not only greatly reduces the first cost 
and maintenance in the latter systems, but eliminates the services 
of an attendant. The elimination of this converting equipment 
will be found from the tables listed on page 382 to lower the first 
cost of a single-phase substation to 27 per cent, and 37.5 per cent, 
of the 600 volt and 1200 volt substations respectively, while the 
operating costs are reduced respectively to 26.2 per cent, and 
58.2 per cent, of the direct current substations. This is not 
clear gain on the part of the single-phase system, however, as it 
is partially balanced by the increased cost of rolling stock in the 
latter system. 

In the relatively few instances in which the increase in dis- 
tribution voltage in the single-phase system is sufficient to permit 
the economical transmission for the entire length of the line at 
trolley potential, the substation cost and maintenance is not 
only entirely eliminated, but the step-up transformers at the 



ALTERNATING VS. DIRECT CURRENT TRACTION 373 

power station may usually be eliminated as well and the switch- 
board considerably simplified in consequence. 

The first cost of the 1200 volt direct current substation is but 
73 per cent, of the 600 volt station because of the lower current 
value necessary for the same output, thereby reducing the size 
and cost of converters, cables and switchboard. 

While the comparisons here made are based on the equipment 
of an interurban railway, the percentages given may be considered 
as approximately representative of the values which would ob- 
tain for heavier service where proportionately higher voltages 
would be used. 

The substation cost per mile of track is somewhat higher for 
the three-phase system than for those systems using a single- 
phase contact line, for reasons which will be discussed in the next 
article. 

Distribution System. — As w^ould naturally be expected, the 
first cost of the distribution system decreases with increase of 
contact line voltages, thereb}^ favoring those systems in which 
high contact line voltages are used, especially in cases where the 
traffic is heavy. 

Commutation and insulation difficulties limit the voltage 
which may be used across motor terminals and therefore the con- 
tact line voltage in the direct current system. Since the contact 
line voltages are necessarily low with this system the distribution 
sj^stem is required to handle large currents, and in order that these 
large currents may be handled without excessive voltage drop 
auxiliary lines or feeders are required. These fines complicate 
the overhead work and greatly increase the cost of the distribution 
system. Stray currents from the track return circuit may cause 
electrolysis troubles which are difficult and costl}^ to mitigate. 

High contact line voltages are easily obtained and readily 
utilized in the systems employing a single-phase contact line. 
The overhead line construction is extremely simple as feeders are 
usually not required. The transmission system and trans- 
former substations even msiy be omitted if the road is compara- 
tively short and the traffic is not too heavy. The distribution 
sj^stem efficiency is higher than with any of the other sj^stems. 
Murray^ gives 97 per cent, as the efficiency of the distribution 
system of the New York, New Haven & Hartford Railroad. The 
operation of a single-phase circuit one side of which is a grounded 

1 A. I. E. E., Vol. XXXI, page 154. 



374 



ELECTRIC RAILWAY ENGINEERING 



track rail produces serious inductive disturbances in paralleling 
telephone and telegraph lines. These disturbances are usually 
even more difficult and costly to mitigate than the electrolysis 
troubles caused by the direct current system. The impedance 
drop in the track rail part of the circuit becomes practically pro- 
hibitive if frequencies higher than 25 cycles are used. This ob- 
jection to the use of the higher frequencies is a very important 
one, particularly where the railway company desires to purchase 
electrical energy from a commercial power company, since the 
generating equipment for commercial power and lighting pur- 
poses is becoming pretty well standardized at 60 cycles. 

The complicated overhead work necessary in the three-phase 
system constitutes a very important objection to that system. 
The difficulty of adequately insulating the complicated overhead 
structures limits the contact line voltage which may be used to a 
comparatively low value. Consequently the number of sub- 
stations and therefore the substation cost per mile of track is 
higher than for a single-phase contact line, although it is still 
much lower than for the direct current system. Practically all 
of the objections which apply to the single-phase system also 
apply to this system. As a result, American engineers have not 
given it very much consideration. 

Of the two most practical systems of distribution, direct cur- 
rent and single-phase alternating current, the single-phase 
alternating current system permits the greatest interchange- 
ability of rolling stock. This feature of interchangeability will 
be discussed further in connection with the article on rolling 
stock. 

Motors. — With the equipment of rolling stock the pendulum 
of efficiency, first cost and possibly of maintenance swings in the 
other direction favoring those systems using direct current 
motors. 

Single-phase motors in their present stage of development are 
generally believed to be slightly inferior to the direct current 
motor in efficiency and quick accelerating qualities for a given 
rating. They are also considerably heavier for a given output, 
thus increasing the weight of car to be accelerated for a given 
traffic return. The above are general conclusions which will 
probably be conceded by both factions that have entered the 
rather extended controversy regarding the relative advantages 
and disadvantages of the single-phase motor for traction pur- 



ALTERNATING VS. DIRECT CURRENT TRACTION 375 

poses. That this question is far from being decided is illustrated, 
however, in the following discussions of the subject before the 
American Institute of Electrical Engineers, which have been 
quoted herein for the double purpose of pointing out the unsettled 
condition of single-phase motor development as well as illustrating 
the various details of design under question. 

Sprague points out the following differences between the single- 
phase and direct current motors.^ 

''1. The input of current in one is continuous, in the other inter- 
mittent. 

"2. One has a single frame, the electrical and mechanical parts being 
integral; the other has a laminated frame contained within an independ- 
ent casing. Hence there is not equal rigidit}^ or eoi-.al use of metal. 

''3. One has exposed and hence freely ventilated field coils; the other 
has field coils imbedded in the field magnets. 

"4c. One has a large polar clearance, and consequently ample bearing 
wear; the other has an armature clearance of about only one-third as 
much, and hence limited bearing wear. 

''5. One is operated with a high magnetic flux, and consequently high 
torque for given armature conductor ciurent; the other has a weak field, 
and consequent lower armature torque. 

''6. One has a moderate sized armature and commutator, and runs 
at a moderate speed; the other, with equal capacity, has a much larger 
diameter of armature and commutator, and runs at a much higher speed. 

"7. One permits of a low gear reduction, and consequently a large 
gear pitch; the other requires a higher gear reduction, and a weaker 
gear pitch. 

''8. The windings of one are subject to electrical strains of one 
character; in those of the other the strains are of rapidly variable and 
alternating character. 

"9. The mean torque of one is the corresponding maximum; the 
mean torque of the other is only about two-thirds of the maximum. 

" 10. The torque of one is of continuous character; that of the other 
is variable and pulsating, and changes from nothing to the maximum fifty 
times a second. 

''11. One has two or four main poles onl}^, two paths only in the 
armature, and two fixed sets of brushes; the other has four to fourteen 
poles, as many paths in the armature, leading to unbalancing, and as 
manj^ movable sets of commutator brushes. 

''12. One can maintain a high torque for a considerable time while 
standing still; the other is apt to burn out the coils, which are short 
circuited under the brushes. 

^ " Some Facts and Problems Bearing on Trunk Line Operation," by 
Frank J. Sprague. A. 1. E. E., Vol XXVI. 



376 ELECTRIC RAILWAY ENGINEERING 

''13. In one, all armature coil connections are made directly to the 
commutator; in the other, on the larger sizes resistances are introduced 
between the coils and every bar of the commutator, some of which are 
always in circuit, and the remainder always present. 

"14. In one the sustained capacity for a given weight is within the 
reasonable requirements of construction; in the other it is only about 
half as much. 

"15. Finally, the gearless type, with armature and field varying 
relatively to each other, is available for one, but this construction is 
denied to the other. 

"Consideration, then, of the characteristics peculiar to each class of 
motor indicates not that the single-phase motor cannot be used, but that 
if adopted the weight or number, and the cost of locomotives or motors 
required to do the work must be much greater; that the depreciation of 
that which is in motion will be much higher ; and that there will always 
be an excess weight of fixed amount per unit which must be carried 
irrespective of the trailing or effective loads. We must, therefore, in 
many cases be led to the selection of the direct current motor, that motor 
which has the higher weight capacity, the greater endurance, and the 
lower cost per unit of power." 

In discussing this paper Storer criticizes each point in turn as 
quoted below. ^ 

"1. 'The input of Current in one is continuous; in the other, inter- 
mittent.' Quite true, but the drawbar pull is quite as effective in one 
case as in the other. 

"2. The direct current motor has a solid frame like the single-phase 
motor. It has, further, two or more laminated poles bolted in, and if the 
interpole construction is used has as many more relatively small and 
delicate poles. The alternating current motor as built by the com- 
pany with which I am connected has, in all sizes up to a diameter of 38 
in. field punchings made in a single piece and built up and keyed in the 
frame, making it as sohd a construction as an armature on its spider. 
The claim for less rigidity in the single-phase motor is, threefore, not 
sustained. 

"3. 'One has exposed and hence freely ventilated field coils; the 
other has field coils embedded in the field magnets.' It is known to 
most motor designers that coils in contact with iron will dissipate heat 
much faster than when in the open air. This is especially true of coils 
in an enclosed motor. I have repeatedly noticed that motor field coils 
which have been removed on account of roasting, have shown the 
insulation in contact with the pole pieces to be in good condition, while 
other sides were badly roasted. I know, therefore, that in respect to 

^ Discussion of above paper by N. W. Storer, A. I. E. E., Vol. XXVI. 



ALTERNATING VS. DIRECT CURRENT TRACTION 377 

ventilation of field coils, the single-phase motor is superior to the direct 
current motor. Smaller cross section of coils also allows the heat to be 
radiated better in single-phase motors, and the fact that a large part of 
the loss in the motor is concentrated in the field iron will enable the 
motor to dissipate a much larger amount of heat for a given temperature 
rise than will a direct current motor. 

"4:. Concerning 'polar clearances.' Many thousands of direct 
current motors are to-day in operation with a clearance of }4 in. to ^q 
in. between poles and armatures, and in practically all cases where more 
than ^f 6 ii^- clearance is used it is for electrical reasons. Further, while 
the smaller air gap used for single-phase motors was at first much feared, 
the fears have proved to be without foundation and the present clear- 
ances of from 0.1 in. to 0.15 in. have proved to be ample and fully as 
good as 0.15 in. to 0.25 in. in direct current motors, because there is no 
unbalanced magnetic pull. 

''5. Concerning 'torque.' The torque of an armature is the pull 
it will exert at 1 ft. radius. Therefore it makes no difference in the 
result whether it is obtained with large flux and few armature con- 
ductors, or vice versa. 

''6. 'A much larger diameter of armature and commutator, and runs 
at a much higher speed.' This is a very general statement: what are the 
facts? The armature diameters ordinarily run from 5 to 15 per cent, 
larger than for direct current motors of corresponding output. It is 
undoubtedly true that the armature speeds of the earlier single-phase 
motors were much higher than the speeds of corresponding direct current 
motors; at the present time, however, the speed at the nominal rating of 
the motor is practically the same as that of direct current motors, and 
the maximum operating armature speeds are within the safe limits set 
for direct current motors. 

"7. Concerning 'gear reduction and gear pitch.' The gear reduction 
depends, of course, upon the speed; and as far as gear pitch is concerned, 
I wish to say that the same gear pitch is used for single-phase motors as 
for direct current motors of the same capacity. 

"8. 'The windings of one are subject to electrical strains of one 
character; in those of the other the strains are of rapidly variable and 
alternating character.' No conclusion is drawn from this. It may be 
of interest to know that there have been a number of instances where 
the single-phase motor has broken down in service on a direct current 
section of the line, necessitating cutting it out of the circuit; but when 
the car reached the alternating current section of the line it has been 
again connected in circuit and operated satisfactorily, thus indicating 
that the electrical strains with alternating current are less severe than 
with direcl: current. 

"9 and 10. Concerning the 'variable torque of the single- phase 
motor.' No comment is made as to the relative merits of uniform or 



378 



ELECTRIC RAILWAY ENGINEERING 



pulsating torque. In a recent discussion before the Institute, Mr. 
Porter called attention to certain characteristics of the torque exerted 
by an alternating current motor, especially when it reaches the slipping 
point of the wheels. It was stated that there is an apparent advantage 
in the pulsating torque, because, when the motor starts to slip it does 
not immediately decrease its mean torque, as is done in the case of the 
direct current motor, but slips in a series of jerks, apparently regaining 
the hold on the rail at every pulsation. 

''11. Concerning the 'number of poles.' The paper states that the 
direct current motor has 'two or four main poles only.' No direct 
current motors built in the last 15 years except those on the New York 
Central locomotives have less than four poles. The paper states that 
the alternating current motor has 'eight to fourteen poles.' The single- 
phase motors built by the company with which I am connected have four 
poles for all sizes up to and including 125 hp. The largest single-phase 
motor thus far built has a capacity of 500 hp. It has but 12 poles. 

"12. Concerning 'a high torque while standing still.' As we under- 
stand the matter, railway motors are designed to move a train rather 
than to hold it at rest. At the same time we know that the single-phase 
motor is amply protected against mistakes of motormen in leaving the 
current on the motor for a half-minute or so with brakes set. 

"13. Concerning 'resistance in commutator leads.' It is well known 
that the resistance leads used in single-phase armatures are for the 
purpose of reducing to a minimum the loss due to the transformer action 
in the short circuited coil. Their presence is fully justified and the 
efficiency is higher than it would be if they were not used. 

"14. This refers to relative weights concerning which I shall have 
something to say farther on. 

"15. On this point I agree absolutely with the author. There is one 
type of construction to which the single-phase motor is not adapted. 
This is so far employed in only a single case. 



Per cent, of full load 
torque 


Direct current 
90 hp. motor 


Alternating 

current, 25 

cycle, 100 hp. 

motor 


Direct current 
200 hp. motor 


Alternating 

current, 15 

cycle, 200 hp. 

motor 


125 


86.25 


82.0 


88.8 


87.3 


100 


86.8 


85.0 


89.0 


88.0 


80 


87.0 


86.0 


89.2 


88.3 


60 


86.5 


86.8 


88.8 


87.7 


40 


85.0 


86.0 


87.0 


85.0 


25 


82.0 


82.5 


84.0 


82.0 



"More or less is said in the paper concerning the lower efficiency of 
the single-phase motor, and inference might be drawn that it is about 



ALTERNATING VS. DIRECT CURRENT TRACTION 379 

10 per cent, lower than that of the corresponding direct current motor. 
Just to show what modern motors are capable of doing, I give above 
in parallel columns the efficiencies of corresponding sizes of direct and 
alternating current motors at different percentages of their full load 
torque." 

Referring to the 1200 volt direct current system for inter- 
urban service, the motors are often of the 600 volt type which has 
been well standardized. Upon the city systems they operate as 
standard 600 volt equipment connected in parallel for full speed, 
while upon the 1200 volt trolley they are connected two in series 
for full speed operation. In cases where only half speed opera- 
tion is required within the city limits, 1200 volt motors similar 
to the 600 volt type are used, the current capacity, of course, 
being less for a given car and extra insulation being provided for 
the higher voltage. 

A number of interurban roads, whose contact line voltages 
range from 1200 to 1500 volts, have been in operation for several 
years and the equipment for these voltages has become pretty 
well standardized. Motors designed for 1200 to 1500 volts 
and connected two in series for operation in connection with 
contact lines whose voltages range from 2400 to 3000 volts 
have not been tried out to the extent that the lower voltage 
equipment has, but those now in service are apparently not 
giving much more trouble than is experienced in the operation of 
600 volt equipment. The increased insulation necessary for 
successful operation on the higher voltages increases the size, 
weight, and cost of the motors, thus diminishing to a certain 
extent some of the advantages direct current motors are assumed 
to have over single-phase commutator motors. 

In the matters of electrical efficiency, simplicity, and ruggedness, 
three-phase motors rank first. They are lighter in weight and 
for a given amount of space have greater continuous output than 
any other form of motor. All three-phase motors now used in 
railway service are of the induction type and therefore have 
shunt type motor characteristics. They operate at approxi- 
mately constant speed for all conditions of load. This feature 
is of value where high schedule speeds must be maintained over 
roadway which has comparatively short, heav>^ grades. Viewed 
from the standpoint of the power plant, however, this feature 
is objectionable because of the peak loads imposed upon it when 
heavy trains are being hauled at high speed over the grades. 



380 ELECTRIC RAILWAY ENGINEERING 

The motors act as generators if operated slightly above their 
synchronous speed, thus permitting regenerative braking on 
the down grades. Their starting characteristics are inferior 
to those possessed by series type motors and therefore they are 
not so well adapted for use in a service where the number of 
stops per mile is large. This, and the fact that small inequalities 
in drive wheel diameters result in serious overloads on the 
motors geared to the wheels with the larger diameters, prac- 
tically precludes the use of this type of motor for all classes of 
service except that of long haul, locomotive drawn trains. 

Rolling Stock. — Two classes of rolling stock, namely, motor 
cars and locomotives, will be compared. 

The added weight and lower acceleration for a given capacity 
of motor are not the only disadvantages of the single-phase 
alternating current system from the standpoint of motor car 
rolling stock. As has been pointed out, it is often desirable 
that cars equipped for alternating current service be able to 
enter cities upon direct current. While the alternating current 
single-phase series motor makes an excellent direct current 
motor, the control equipment for use upon either system is at 
best rather complicated and its first cost, weight and maintenance 
relatively high. The added complication of this combined control 
is at once obvious if a comparison be made of Figs. 143 and 149, 
while the tables listed under the caption ''First Cost, Mainte- 
nance, Operating Expense" prove the rolling stock thus equipped 
to cost 28 per cent, more, with a probable maintenance charge 
of 49 per cent, more than the 600 volt direct current equipment. 

Since the three-phase and split-phase systems make use of 
three-phase motors, they are not very well suited for motor car 
operation. 

Single-phase rectifier motor cars should be ^ little lighter than 
straight single-phase cars, have about the same overall efficiency, 
and would possess the excellent accelerating characteristics 
of the direct current car. The rectifier set would take up some 
valuable floor space, however, and the maintenance charges 
would be higher than for the direct current car. 

In the matter of locomotive weights, there seems to be little 
difference between the direct current and the three-phase systems. 
Single-phase and split-phase locomotives are somewhat heavier 
although the differences are not great. Inasmuch as it is 
sometimes necessary to ballast electric locomotives in order to 



ALTERNATING VS. DIRECT CURRENT TRACTION 381 

get sufficient adhesive weight, the sHghtly greater inherent 
weights of the single-phase and spht-phase locomotives are 
not so much of a disadvantage as they might seem on first 
thought. 

As regards flexibilit}^, single-phase and split-phase rectifier 
rollling stock rank highest since they may be used in connection 
with any kind of a distribution system. When used in con- 
nection with the direct current distribution system, however, 
additional control equipment must be provided. Since the 
voltage over the motors in these two sj^stems may be varied by 
means of adjustable ratio transformers the control losses are 
minimum and a large number of efficient running speeds are 
possible. 

Alternating current rolHng stock costs more and has higher 
maintenance charges than direct current rolling stock. Also 
as regards reliability, published reports indicate that the direct 
current rolling stock has the advantage, although on account of 
the widely different operating conditions which exist on the dif- 
ferent roads, fair comparisons are hard to make. Some data 
on the reliability of electric motive power are given in the next 
chapter. 

Power Factor. — One of the disadvantages of the alternating 
current sj^stems is the low, uncontrollable power factor. The 
direct current system has no apparatus on the car or between the 
car and the converters which can low^er the power factor and 
its converters may even permit the power factor of the trans- 
mission line to be raised. The alternating current systems with 
no synchronous converting apparatus offer no means of power 
factor control, while the power factor is lowered still further 
beyond the substation by car motors, transformer, steel mes- 
senger or trolley, if used, and rails. A lower power factor means 
higher proportional current for a given capacity with increased 
first cost of equipment and percentage losses. 

Frequency. — Another much discussed factor is that of fre- 
quency if the single-phase system is being considered. Al- 
though a frequency of 25 cycles has been standardized for power 
supply and lower frequency apparatus is at present special and 
therefore high in first cost and slow of delivery, the introduction 
and future standardization of a 15 cycle frequency for railway 
service has been seriously advocated by many railway engineers 
for the following reasons. 



382 



ELECTRIC RAILWAY ENGINEERING 



1. An increase of from 30 to 40 per cent, in output of a motor 
of given size. 

2. Consequent reduction in motor capacity required. 

3. Consequent reduction in first cost of motor equipment. 

4. Higher motor efficiency. 

5. Higher motor power factor. 

6. Better commutation. 

7. Less dead weight on axles. 

8. Lower line losses. 

In contrast to these advantages of low frequency may 
be listed the impossibility of supplying lighting loads from 
the same generators with this frequency, the already estab- 
lished standard of 25 cycles, unsatisfactory turbine design 
in small sizes and the higher first cost and greater weight of 
transformers. 

First Cost, Maintenance and Operating Expense. — The 
relative merits of the direct current and single-phase systems 
for interurban service from the standpoint of first cost, mainte- 
nance, and operating expenses can best be illustrated by means 
of tables XLI and XLII taken from a very able discussion of the 
subject before the American Institute of Electrical Engineers 
by W. J. Davis, Jr. 1 



Table XLI. — Comparative Cost per Mile Single Track 



D. c. 600 V. D. c. 1200 v. A. c. 6600 v. 



Road bed, complete including grad- 
ing, ballasting, etc. 

Trolley and feeder installed 

Track bonding 

Transmission line installed 

Substation installed 

Power station installed 

Cars and equipment 

Telephone 



Saving over 600 volts d. c. 



$15,000 

3,800 
600 
1,500 
2,200 
2,450 
1,800 
120 



27,470 



$15,000 

3,000 
530 
1,500 
1,600 
2,450 
1,970 
120 



26,170 
1,300 



$15,000 

2,100 
480 

1,300 
600 

2,570 

2,300 
120 



24,470 
3,000 



^ "High Voltage Direct Current and Alternating Current Systems for 
Interurban Railways," by W. J. Davis, Jr., A. 1. E. E., Vol. XXVI. 



ALTERNATING VS. DIRECT CURRENT TRACTION 383 

Table XLll. — Relative Operating Cost per Mile Single Track per 

Annum 
(One hour headway) 



D. c. 600 V. 


D. c. 1200 V. A. c. 6600 v. 


Car miles per day 

Kw. hours per day at power house . . 


64 
275 


64 
275 


64 

245 


Cost of coal per annum 

Cost of substation attendance 

Maintenance of motors and control.. 


$470 
175 

94 


$470 

79 

117 


$419 

46 

140 


Total 


$739 


666 
76 

137 


605 


Saving over 600 volts direct current 

exclusive of fixed charges. 
Saving in fixed charges. . . 


134 




315 








Total annual saving.. . 




$213 


449 











The above comparative costs are based upon the following 
data: 

Length of road, 50 miles or more. 

Cars, 52 ft. over all, weighing 21 tons, without equipment or 
load and seating 56 passengers. 

Car equipment, four 75 hp. motors. 

Maximum speed on tangent level track, 45 m.p.h. 

Schedule speed, 24 m.p.h. including stops and slow running 
through towns. 

Headway, maximum service, 3^^ hour. 

Frequency of stops, one in 2 miles. 

Average energy, 85 watt hours per ton mile at car. 



D. c. 600 V. D. 



1200 V. 



I A. 



6600 V. 



Spacing of substations 

Maximum trolley voltage drop 

Efficiency, generator bus bars to cars 
Average efficiency car equipment . . . 
Average power factor of system .... 



10 miles 
25 per cent. 
71 per cent. 
75 per cent. 
96 per cent. 



22 miles 
25 per cent. 
71 per cent. 
75 per cent. 
96 per cent. 



32 miles 
10 per cent. 

84 per cent. 
73 per cent. 

85 per cent. 



The following table^ compiled by H. L. Kirker from Interstate 
Commerce Commission reports, compares the operating ex- 

1 Electric Journal, Nov., 1914. 



384 



ELECTRIC RAILWAY ENGINEERING 



penses of several high class interurban roads. The single-phase 
road has been in operation 10 years and was the first single- 
phase road built in the United States, yet it makes a very 
creditable showing when compared with some of the newer 
high voltage direct current roads. 

Table XLlll. — Operating Expenses of Interurban Railways 



Name of road 



Kind of 
current 



Voltage 



Ave.cts. 

per car 

mile 



Time 
period 



Indianapolis & Cincinnati Traction Co. 

Washington, Baltimore & Annapolis R.R. 
Pittsburgh, Harmony & Newcastle Ry. . . 

Aurora, Elgin & Chicago Ry 

Ft. Dodge, Des Moines & Southern R. R. 

Oregon Electric Ry 

Central California Traction Co 

Scioto Valley Traction Co 

Otsego & Herkimer R.R 

West Penn Railways 



Single- 
phase a. c. 
D. c. 
D. c. 
D. c. 
D. c. 
D. c. 
D. c. 
D. c. 

D. c. 
D. c. 



3300 

1200 
1200 

600 
1200 
1200 
1200 

600 

600 
600 



18.8 

19.9 
19.3 



18, 
20 
29 



27.0 
20.7 



30.1 
22.5 



1911-14 

1911-13 
1911-13 
1911-13 

1913 
1911-13 
1912-13 
1910-11 
& 1913 
1910-13 
1910-13 



Several steam railways in the United States have electrified 
certain sections of their lines, yet very little authentic detailed 
cost data have been published. In some cases steam locomotives 
still operate over certain portions of the electrified sections 
making it almost impossible to segregate operating costs. Many 
of the installations have been more or less experimental and 
their first costs contain heavy development charges. A study 
of the scattered data relative to American railways which have 
been published indicates that: 

(1) The energy costs for the various systems are not far from 
equal, favoring if anything the alternating current systems. 

(2) In the direct current system a large portion of the in- 
stallation cost is in the feeder system and converting apparatus, 
and that substation maintenance and attendance expenses are 
important items in the list of operating expenses. 

(3) The locomotive first costs and maintenance for the single- 
phase system are higher than for the direct current system. 

(4) The first cost of the single-phase system is from 5 to 15 
per cent, less than that of the direct current system. 

(5) The operating expenses for the two principal systems, 
single-phase and direct current, are approximately the same. 



ALTERNATING VS. DIRECT CURRENT TRACTION 385 

Operating conditions in Europe are different than in America, 
nevertheless it is interesting to note that the Swiss Commission, 
before alluded to, in their report to the administrative council of 
the Swiss Federal States Railway, made early in 1914, rec- 
ommended the installation of a 10,000 volt, 15 cycle, single- 
phase sj^stem. The commission, which was composed of 
eminent engineers, after an exhaustive study which extended 
over a period of 5 years and in which consideration was given to 
direct current with contact line voltages up to 3000, three 
phase up to 8000, and single phase up to 15,000 volts, con- 
cluded that both from the technical and economic points of 
view, the recommended system was best adapted to the par- 
ticular needs of the Swiss State railways. They found that 
the ultimate j&rst costs of the systems were approximately the 
same; that locomotives of adequate power could be obtained 
with any of the systems above named and gave preference to 
the single-phase system on the ground of its greater flexibility. 
Commissions for the Prussian, Bavarian, Austrian, and Swedish 
governments have turned in very similar reports. It seems 
therefore that in continental Europe, Italy excepted, the single- 
phase system is likely to become pretty well standardized. 

The present tendency everywhere is toward the use of higher 
contact line voltages. This is markedly true for the direct 
current system in which voltages proposed for use to-day are five 
times the values used a decade ago. Single-phase alternating 
current apparatus has been greatly improved during the last few 
years and the introduction of the various combined systems has 
tended to broaden the field of the single-phase contact line. 
Most electrical engineers agree that no one electric system is 
best adapted to all classes of service and they disagree most 
markedly as to the type of system which should be used for any 
given set of operating conditions. The fact remains, however, 
that any one of the systems will do the work of any railway in a 
very satisfactory manner. The need of standardization is 
urgent, for if the electrified terminal and tunnel divisions of 
trunk lines expand to the point where they desire to merge and 
exchange equipment to give through service over several roads, 
the use of 600 volt direct current third rail by one railway, 
of high voltage alternating current by a second, of three 
phase by a third, of high voltage direct current by a fourth 
will result in a situation fully as serious as the attempted com- 

25 



386 • ELECTRIC RAILWAY ENGINEERING 

bination not long ago of roads of different track gauges and of 
cars with and without standard air brake equipment. The late 
George Westinghouse did not sound the warning of standard- 
ization any too early, therefore, in his paper before the joint 
meeting of the American Society of Mechanical Engineers and 
the British Institution of Mechanical Engineers, held at London 
in 1910, when he said: 

''For the present it may be a matter of little moment whether 
different systems have their contact conductors in the same 
position, or whether the character of the current used is the same 
or different. As previously stated, in the early days of railroad- 
ing, it was of little consequence whether the tracks of the dif- 
ferent systems in various parts of the country were alike or un- 
like, but later it did make a vital difference and the variation 
resulted in financial burdens which even yet lie heavily on some 
railways. It is this large view into the future of electrical 
service which should be taken by those responsible for electrical 
railway development." 



CHAPTER XXVIII 
ELECTRIC TRACTION ON TRUNK LINES 

The late E. H. Harriman is quoted in the New York Times 
as having said: 

''But perhaps it is chimerical to think now of rebuilding the 
railroads of the entire country, and of replacing the entire rail- 
road equipment. If so, what is the best thing? Obviously, 
electricity. And I believe that the railroads will have to come 
to that, not only to get a larger unit of motor power and of dis- 
tributing it over the train load, but on account of fuel. That 
brings up another phase of the existing conditions. We have 
to use up fuel to carry our fuel, and there are certain limitations 
here just as much as there are in car capacity or motive power, 
particularly when you consider the distribution of the coal pro- 
ducing regions with respect to the major avenues of traffic. The 
great saving resulting from the use of electricity is apparent, 
quite aside from the matter of increasing the tractive power and 
the train load. 

''The only relief which can be obtained through economics 
of physical operation must come through the outlay of enormous 
amounts of money such as would be involved in a general electri- 
fication or change of gauge." 

This statement coming from such an eminent steam railroad 
authority, together with the fact that a number of sections of 
trunk line railroads throughout the country are now electrified 
must convince the most prejudiced opponent of electrification 
that the time has come for the serious study of the problem of 
trunk line electrification. 

A study of Table XLIV, in which are listed the more important 
steam railway electrifications, indicates that in the earlier electri- 
fications electric motive power was adopted to meet special re- 
quirements or to solve peculiar problems in traction, such as the 
necessity of increased service in large terminals, avoidance 
of smoke in tunnels, increase in safety of operation, and increase 
in track capacity on mountain grades, but that in later electrifica- 
tions economy of operation has been one of the chief reasons. 

387 



388 



ELECTRIC RAILWAY ENGINEERING 



o o 

ID VJj 



at 



°-3 






CI O 






lO 0) m 

-^^ -o "o 

r » r c3 

o 'S 1 

g 6 9. 2-2 

O .-5 O -iJ O 'm 

^: ^ 2 ft gg -^ 



-*j o ^ o 

03 u ? <D 

O ^ H ^ 



03 >i S >> 



03 t^ 03 tH 

o ^ o -*" 



03 >i 03 >i 

£3 a; fl <u 

03 tn C3 k< 

o ^ o ^ 



^ (D • 

^ "o Z 
?< ^ r 

W) (N -73 



-^ lo a (N 

« - a; ^ 

.S o H o 
to o 



o o 

O «D 



o 


O 


O 


lO • 


■^ 


(N 


lO 


o 


<N 


(N 


a> 


05 



;--i ;h m I ™ 

05 Ol T3 T}< 2 

- - pq 55 fq 



03 M 



Q o 



3 oj a> 
H H H 



IH O 



"m .2 "aJ 

figs 
fi ^ s 

H H H 



« I i 



-1^ 

C ** o 
CI ^ c 



-s .S 

^ s 



S S 

M O 

a 



>i a> 03 



ft M 



(B og aj 






b So 

a 



=a a! «8 



(D CO 






03 y3 

2J 

o 
a; 

s 

oJ 
1^ 



s I 

o" 

o 



03 0) 

fl (D a> 

^ ^ o 

>^ . ^ 

hJ -^ ►S 

r>H r 

rt .1? rt 



S 

2 =< 

W ^ 

■^ 03 

CLi 03 

^- o 

Ph .i3 CI o 

^ ,f2 a) M 

CI O -a S 

T3 rH- ^ t> 



Pi 2 



O 



•^ s ^' ;s 



13 aj (0 

« ^- s s 

O Cl k^ -73 

03 H ^ O 

a a) p '^ 



g|s 



2 ^ ° ■ - 

I rt 1 1 



—(."So 
S o f^ 

o) o o 
c .S 2 

^ ■ 3 



O 



I "^ n 



o ° 



Ph Pl, 



fi . _ a) 



o« 



ELECTRIC TRACTION ON TRUNK LINES 389 

Probably the two paramount questions in the minds of steam 
raih'oad directors in connection with this problem are: 

1. Can the service be improved with electric traction? 

2. What will it cost to change and to operate and maintain 
the new system when installed? 

While it seems advisable to consider these questions more in 
detail subsequently, a few of the minor advantages of electric 
traction which are involved in the first question of possible 
improved service, will be first considered. The outline which 
forms the basis of the following brief discussion on these advan- 
tages is one presented in great detail in the very valuable paper 
by Messrs. Stillwell and Putnam before the American Institute 
of Electrical Engineers.^ 

The factors which contribute to the earning power of the elec- 
trified road to a greater extent than the steam railroad are: 

Frequency of service. 

Speed. 

Comfort of passengers. 

Safety. 

Reliability of service. 

Increased capacity of line. 

Frequency of stops. 

Convenient establishment of feeder lines. 

Frequency of Service. — Experience with high speed inter- 
urban lines paralleling steam lines, but offering much more fre- 
quent service as illustrated in Table III, Part I, leads to the 
conclusion that frequent service creates traffic and therefore 
increases earning power. The frequent service offered by 
an electrified system is usually impractical with steam operation. 

Speed. — Higher average speeds are possible and practical in 
electric service for four principal reasons. 

(a) The absence of reciprocating parts reduces danger of the 
locomotive leaving the track. 

(6) The absence of reciprocating parts reduces the maintenance 
of the track and the liability of broken rails. 

(c) The more rapid acceleration permits higher average speed 
with the same number of stops, or more stops with the same 
schedule speed. 

(d) For heavy trains requiring two locomotives, high speeds 

^ ''On the Substitution of the Electric Motor for the Steam Locomotive," 
by Lewis B. Stillwell and Henry St. Clair Putnam, A. 1. E. E., Vol. XXVI. 



390 ELECTRIC RAILWAY ENGINEERING 

can be maintained by means of the multiple unit control system. 
This is unsafe with two steam locomotives, as both engines cannot 
be controlled by a single engineman. 

Higher speeds can be maintained over mountain grades with 
electric locomotives than can be maintained with steam loco- 
motives. On ascending grades, the speed at which a steam loco- 
motive can haul a given weight of train is limited by its boiler 
capacity and by the fact that a great deal of power is required to 
haul the heavy locomotive itself when it is operated at high 
speed on a heavy up grade. On the other hand exceedingly 
powerful motors can be mounted on a comparatively^ light 
electric locomotive. These motors can carry large overloads 
for short periods of time and they receive their energy supply 
from a large power station. On down grades regenerative brak- 
ing is possible, thus permitting the air brakes to be reserved for 
emergency service and higher speeds to be used with safety. 

Comfort of Passengers. — The general comfort of passengers 
is greatly enhanced by the following features of electric traction : 

(a) Elimination of smoke and cinders. 

(Jo) Improved ventilation of cars made possible because of the 
absence of smoke and cinders. 

(c) More efficient and satisfactory car lighting possible, al- 
though unfortunately not always provided. 

{d) Easily controlled car heating. 

Safety. — Several very notable elements of danger which are 
present in steam traction are eliminated when electric motive 
power is used. 

(a) The power may be shut off by the train dispatcher to avoid 
collision. 

(fo) The results of the absence of reciprocating parts which 
permit higher speeds to be maintained as outlined under the 
caption '^ Speed" also reduce the probability of accident. 

(c) If a collision occurs, the power may be promptly cut off if 
it is not accomplished automatically, as is usually the case. 

{d) The absence of the intense fire of the locomotive reduces 
the probability of fire in the wreckage. 

(e) The elimination of hot water and steam in locomotive and 
heating system reduces the dangers often resulting from such 
sources. 

(/) The absence of smoke and steam prevents errors in reading 
these signals from these causes. 



ELECTRIC TRACTION ON TRUNK LINES 391 

(g) Less likelihood of fire from electric lighting than from the 
oil or gas lamps commonly used upon steam roads. 

(h) The presence of a source of electrical power along the 
roadway and the necessary employment of electrically trained 
maintenance crews should decrease the first cost and maintenance, 
and therefore increase the use of automatic block signals. 

The locomotive driver can give his entire attention to driving; 
he is not required to engineer a large steam power plant. His 
seat can be so located that both sides of the track are in full view 
at all times. 

As has been noted under a preceding caption regenerative 
braking is possible, and since the air brakes then are used only 
in stopping the train, car wheels and brake shoes are not heated 
by long continued applications of the brakes while the train is 
descending a heavy grade. The number of wrecks due to 
broken wheels, cracked by such heating is thus reduced. 

Excessive wheel loads, which are common causes of track 
failure, can be avoided. Fire risks on property adjoining the 
right-of-way are decreased and there are no stray sparks to 
cause prairie or forest fires. 

It must be remembered, however, that in contrast to these 
advantages, the electrical distribution system, especially the 
third rail, offers a danger not present in steam railroad operation. 
Whereas the third rail may be protected, thereby reducing the 
danger under normal operation to a minimum, such protection 
would avail little in the case of a wreck. Under these circum- 
stances the automatic circuit breakers must be relied upon to 
disconnect the section from the source of supply before serious 
physiological effects are produced or fires started in the wreckage. 

Reliability of Service. — Comparison of the train delays from 
all causes, both electrical and mechanical, before and after elec- 
trification upon the few roads which have been operating suffi- 
ciently long by electricity to guarantee dependable results, points 
to the conclusion that the service is more reliable after electri- 
fication than before. 

For example, upon the Manhattan division of the Interborough 
Rapid Transit system of New York after electrification, the 
delay during the most severe months of the year for the exposed 
third rail system was but 72 per cent, of that under steam 
operation, expressed in train minutes, although an increased car 
mileage of 37 per cent, was maintained with the electric service. 



392 



ELECTRIC RAILWAY ENGINEERING 



Upon the electrified section of the New York, New Haven 
& Hartford Railroad during the heaviest traffic day of the year 
occasioned by the annual football game at New Haven, 128 
regular trains and 30 special trains were operated between New 
York and New Haven in 1908 with but two delays totaling 17 
minutes, while in 1909, 155 trains were run with no delays 
whatever. 

The following table ^ compares the total delayed time on the 
Butte, Anaconda & Pacific Ry. for the month of June, 1913, 
steam operation, with the month of June, 1914, electrical 
operation. 

Table XLV. — Comparison of Train Delays 





Numbe 


r trains 


Total delay 


Grand total 




Freight 


Pass. 


Freight 


Pass. 


Hr. 


Min. 




Hr. 


Min. 


Hr. 


Min. 


1913 
1914 


357 
280 


272 
280 


497 

296 


34 

28 


20 

7 


46 
10 


518 

301 


10 

38 


Percent, 
decrease 


21.51 


2.941 


40.4 


75.12 


41.78 



^ Increase. 

For the year 1912 the average locomotive mileage per train 
detention chargeable against motive power on the electrified 
division of the New York Central & Hudson River Railroad was 
48,271 miles, and the maximum mileage made by any one loco- 
motive without detention was 249,423 miles. ^ A comparison of 
many published reports indicates that, on the average, train 
detentions chargeable against motive power with electric opera- 
tion are only about 50 per cent, of the number occurring with 
steam operation. 

Increased Capacity of Line. — One of the marked advantages 
of electric traction is its large tractive effort for a given size 
and weight of equipment. While this feature is pronounced in 
the electric locomotive because of the elimination of the tender 
and the possible use of such a design as to throw practically all 

^Abstracted from "The Electrical Operation of the Butte, Anaconda & 
Pacific Ry., J. B. Cox, A. 1. E. E., Nov., 1914. 

2 Quereau, in Ry. Master Mech. Assn. Proceedings, 1913. 



ELECTRIC TRACTION ON TRUNK LINES 393 

the weight of the locomotive upon the drivers, the effect is still 
more marked if motor cars be used, thus making practically the 
entire weight of train available for tractive effort between wheels 
and track. With this relatively great tractive effort much 
higher rates of acceleration are possible, which in turn permit 
smaller headway between trains and increased traffic capacity 
for a given track. 

This is of particular value upon heavy grades of the single track 
roads of the West, where electrification permits so great an 
increase in traffic over an existing single track that it obviates 
the necessity of double tracking the road for some time to come. 
In this case the cost of electrification may be balanced directly 
against the cost of a second track, which in the mountains of the 
West becomes a formidable figure. 

In tunnels the capacity of the track is increased because no 
time interval between trains is required for tunnel ventilation. 
With steam locomotives the vitiated air so affects the operation 
of the furnace that the locomotive capacity is often considerably 
reduced. 

Further, the length of freight trains using the steam locomotive 
is limited by the strength of the draft gear. With the use of two 
or more electric locomotives at the head of a train, or if the limit 
of the draft gear is reached, possibly the introduction of several 
locomotives throughout the length of the train, all operated by 
means of the multiple unit control from the leading engine, will 
probably make possible a greatly increased freight traffic over a 
given road, thus increasing the freight as well as the passenger 
capacity of the line. 

Frequency of Stops. — The ability of the electrically operated 
train to make more frequent stops and thus better accommodate 
the riding public without reducing the schedule from that of the 
steam road has already been explained. 

In addition to the above advantage, in some instances it is pos- 
sible to interconnect the local railway system with the electrified 
road in such a way as to transport passengers more nearly to 
their destination without change. 

Both of the above features tend to increase the traffic and 
resulting earnings of the road. 

Convenient Establishment of Feeder Lines. — With the re- 
duced cost of power possible with an electrified trunk line, short 
branches of present steam roads or existing suburban or inter- 



394 ELECTRIC RAILWAY ENGINEERING 

urban lines may be operated electrically much more economically 
than at present. The large and efficient organization of the trunk 
line system also adds materially to this possibility. These short 
branch roads then become valuable feeders to the through trunk 
line. 

Still further economy and convenience to passengers in such 
branch line operation may often be brought about by adding 
branch line motor cars to the through train at junction points, 
operating the entire train thus made up by the multiple unit 
system. 

Improvement of Service. — It is believed that the first question 
to be asked by the directors of a steam road, to which reference 
was made early in the chapter, has been satisfactorily answered 
by the above improvements in the service, which have been shown 
to be possible upon electrified roads. 

The factors, adaptability to service, possibility of increased 
drawbar pull and more rapid acceleration should, however, have 
more detailed analysis, for it is largely with regard to these fea- 
tures that service may be improved and earnings increased, and 
therefore it is these features to which the present steam rail- 
road officials look at a time when service can no longer be increased 
with present locomotives since the latter have practically reached 
their maximum size and efficiency. 

Tractive Effort and Drawbar Pull. — In Fig. 186 are plotted 
the speed tractive effort curves for several modern steam and 
electric freight locomotives. The weight of the tender is in- 
cluded in the steam locomotive weights and all of the electric 
locomotives are double unit machines. The data, from which 
the curve for the steam Mallet was plotted, were taken in the 
course of some tests by the Southern Pacific Railway on one of its 
largest oil burning locomotives.^ The curve for the Mikado 
type locomotive was calculated from the dimensions of a typical 
locomotive of that type as built in the year 1913. The single- 
phase locomotive units are of the type used by the New York, 
New Haven & Hartford Railroad for mixed service and are 
geared for higher speeds than are usually practicable in heavy 
mountain freight service. The three-phase units are of the 
type used by the Great Northern Railway in its Cascade tunnel 
electrification and the direct current units are the Butte, Ana- 
conda & Pacific type which were described in Chap. XXVI. 

^ Railway Age Gazette, Jan. 14, 1910. 



ELECTRIC TRACTION ON TRUNK LINES 



395 



The three-phase locomotive has but one running notch on the 
controller; the direct current has two, and the single phase, with 
its' adjustable ratio transformer control has thirteen. The 
single-phase locomotive can, therefore, economically exert its 
rated tractive effort through a very wide range of speeds. The 
curves for the steam locomotives are for the condition of maxi- 
mum continuous boiler output with boiler new and clean. As the 



4& 

40 














1 








\ 


Curves: 






A 


*1 - 160 Ton Direct Current Locomotive 




35 




R 








\ 


^3-305 Ton Steam Mallet Locomotive 








w 


* 4 - 226 Ton Steam ilikado Locomotive 
*5 - 220 Ton Single Phase Locomotive 




30 


\ \ 






\ \ 












\ 


\ V^^"^- 










k' 


\ 


Y4\ 










\ 




\^5j 








1 
I20 


\ 


s^l \ 


•"v 


\ 










\^V\ 


^\ 


Ns^ 






15 


*2 


iVs\ 


IHr. iH 


1 








\c 


\*3 


1 
1 


1 
1 




10 


' \ 


\ 


1 


1 




\ 


\ 


1 


1 




5 


\ 


\ 

a 



S 


1 


li 

£ 1 




i 


< 


1 \ 


<! 

1 
1 





20 40 60 80 100 120 

Tractive Effort,. Thousand Pounds 
Fig. 186. — Locomotive speed-tractive effort curs^es. 

tubes and other heating surfaces quickly become fouled in service 
the curves for average working conditions would show lower 
tractive efforts. Leaky tubes also seriously affect the boiler's 
capacity and it seems to be a difficult matter to keep the tubes 
perfecth^ tight on account of the high furnace temperatures 
used in the operation of modern boilers. 

The points, marked C and ''l Hr." on the electric locomotive 
curves indicate the continuous and 1 hour ratings respectivel3^ 



396 



ELECTRIC RAILWAY ENGINEERING 



The Mallet, direct current, and three-phase locomotives are 
low speed machines designed for hauling heavy trains over 
mountain divisions. On account of the numerous sharp curves 
it is impracticable to operate heavy trains at higher speeds over 
these divisions. 

A study of the curves leads to the conclusions: 
1. The curves for the electric locomotives are more nearly 
horizontal than those of the steam locomotives. The physical 
significance of this is that a change in the drawbar pull of a 
steam locomotive is accompanied by a much greater change 
in speed than a similar change causes in the speed of an electric 



50 



40 



g30 



20 



10 



^ 


^ 


::^^ 
















\ 


^\ 


^ 




















^ 




^ 


^^ 


-^ 


Curves 

* 1 160 Ton Direct Current LocomotLv.e 

* 2 230 Ton Three Phase Locomotive 
*^3 305 Ton Steam Mallet Locomotive 




\ 


^ 


-^ 














\ 


\ 


x^^ 





















Fig. 187. 



2 3 4 5 6 

Per cent Grade 

-Effect of grades on drawbar pull. 



locomotive. Roughly classified, electric locomotives are con- 
stant speed machines. 

2. For a given weight of locomotive the starting tractive 
effort of the electric locomotive is much higher than that of its 
steam competitor. 

3. The electric locomotive can exert a tractive effort up to the 
limit fixed by adhesion when running at a comparatively high 
speed. 

By reason of its constant speed characteristics and its light 
weight for a given tonnage rating, the electric locomotive main- 
tains its speed while ascending grades much better than does 



ELECTRIC TRACTION ON TRUNK LINES 397 

the steam locomotive. Uniformity of speed tends to simplify 
train schedules, reduce the danger of collision and increase 
the capacity of the track. Where the profile of the road is un- 
dulating, a short heav}^ grade often fixes the tonnage rating of a 
steam locomotive. The electric locomotive by reason of its 
ability to carry large overloads for short periods af time is not so 
badly handicapped in this respect. It is not only able to start 
its train on a heav}^ grade, but it is also able to carry it over the 
grade at nearly rated speed. On the other hand the steam loco- 
motive maintains its tractive effort over a wide speed range much 
better than does the electric, and thus enables the same loco- 
motive to be used successfully in hauling trains whose scheduled 
speeds are widelj^ different. 

Fig. 187 shows the effect of grades on the drawbar pulls of 
the three locomotives which are shown in Fig. 186 as having 
practically the same speed when exerting a tractive effort of 
60,000 lb. On account of its great weight the drawbar pull of 
the steam locomotive decreases very rapidly as the per cent, 
grade increases. On a 3 per cent, grade the drawbar pull of 
the direct current locomotive is 35 per cent, greater than that 
of the Mallet. 

Tonnage Ratings and Service Capacities. — The tonnage 
ratings, on a IJ2 pei' cent, grade, at various speeds, of the loco- 
motives whose speed tractive effort curves were given in Fig. 186 
are plotted in Fig. 188. The points C and "1 Hr." have the 
same significance as in Fig. 186. Tonnages lower than the con- 
tinuous rating may of course be hauled continuously, but ton- 
nages higher than the 1 hour rating can be hauled onl}^ for a 
short time. The continuous tonnage rating of the 160 ton direct 
current electric locomotive is practically equal to that of the 305 
ton Mallet at 16 m.p.h. However the thing of most interest to. 
the operating man should be, not the tonnage which can be 
hauled by a single locomotive but rather the service capacity or 
the number of ton miles per hour which the locomotive can haul 
over a given track. The service capacity may be calculated by 
the equation, 

a • V + v/ u v/ running time 
Service capacity = tonnage X m.p.h. X ^ ^ ^ r- 

The service capacities, on a 1 J-^ per cent, grade, of the locomotives 
under discussion have been plotted in Fig. 189. The ratio of 
running time to total time is affected by a great many factors 



398 



ELECTRIC RAILWAY ENGINEERING 



most of which are more or less variable so that only determination 
of an average ratio can be made for a given road. The ratios 
here used, %o for steam and %o foi" electric, are probably high 
for many roads but are the values found to obtain approximately 
in at least one electrification study. 

It will be seen from the figure that the curves for the two 
kinds of locomotives are very different. The curves for the 
steam locomotives reach maximum values at definite values of 



40 



35 



25 



15 



10 



\ 














\ 


c 

\ 


Curves: 

*1 -160 Ton Direct Current Locomotive 
*2 - 230 Ton Three Phase Locomotive 
*3 - 305 Ton Steam Mallet Locomotive 
*i - 226 Ton Steam Mikado Locomotive 
*5 - 220 Ton Single Phase Locomotive 






y VHr. 




\ 


V^ 


\«6 


^ 








*2 ' 




V^,- 


Hr. 












V 


\^3 












\ 




\ 





















5 10 15 20 25 

Trailing Tons, Hundreds 
Fig. 188. — Locomotive tonnage ratings. 



30 



speed, while those of the electric locomotives have no definite 
maximum values except those fixed by the ratings of the re- 
spective locomotives. The same statement may be made re- 
garding the tonnage rating curves in Fig. 188. The service 
capacity of the Mallet is greatest at a speed of about 123-^ m.p.h. 
and at this speed it has only about three-fourths of the con- 
tinuous capacity of the 160 ton electric locomotive. 

The curves for the direct current and single-phase locomotives 
are plotted for the operating conditions which obtain when 



ELECTRIC TRACTION ON TRUNK LINES 



399 



the controller handles are in the last running notch. It will be 
remembered that the single-phase locomotive has twelve and 
the direct current one other running notch. Curves for the 
lower speed notches will be located to the left and down from 
the curves here given. The locus of the continuous rating point 
"C" of the single-phase locomotives is the line AC. The inter- 
section of AC and the curve for the Mikado locomotive gives 
the speed at which these two locomotives, which have about the 
same weight, have the same service capacity. If the gear 

40 



35 



30 



25 



15 



10 





\ 


\ 


Curves: 




\ 


\ 


*1 - 160 Ton Direct Current Locomotive 




\ 


\ 


*2 - 230 Ton Three Phase Locomotive 
*3- 305 Ton Steam Mallet Locomotive 




i \ 






\ \ 


C*4- 226 Ton Steam JkTikado Locomotive 






\ 


\*5- 220 Ton Single Phase Locomotive 






\ 


\ 






V 


•5\ 


V^Hr. 




\ 


yi 


/ 


♦4 








^ 




\/ 












^"^^^ 


*2 


1 
— 1 — 


1 


M 


^"---^^c 


. IHr. 








/ 


/ ) 


C 


iHr. 








/ 


/ -a/ 










/ 




/ 










A 


/ ^ 


/ 

























8 12 16 20 

Ton-Miles per Hour, Thousands 



24 



28 



Fig. 189. — ^Locomotive service capacities. 

ratio, drive wheel diameter and rated motor speed of the single- 
phase locomotive had been the same as those of the direct 
current locomotive their service capacity curves would be 
approximately coincident. If, therefore, it is desired to change 
the speed at which an electric locomotive has its maximum 
continuous service capacity it may be readily done (within certain 
limits) by changing the gear ratio of the locomotive. 

Accelerating Qualities. — The ability of the electric locomotive 
to accelerate a train quickly jg well illustrated in Fig. 190. These 



400 



ELECTRIC RAILWAY ENGINEERING 



curves were calculated for a trailing load of 750 tons, consisting 
of seven steel Pullman cars, three steel coaches, and two baggage 
or express cars, ascending a J^ per cent, grade. The locomotives 
used are among the latest and most powerful of their respective 
types. The curves show that the electrically hauled train is 
pretty well up to the balancing speed in 100 sec. and prac- 
tically reaches that speed in 200 sec. 

The Pacific type steam locomotive has approximately the same 
balancing speed but does not reach it until about 900 sec. after 
starting. The Atlantic type locomotive balances at a lower 
speed and does not accelerate as rapidly as the heavier Pacific 



60 




^ 




A 












50 
















/ 






B^ 












40 
30 
20 
10 










/ 


/ 




c^^- 












/ 


/ , 


/ 






A - 110 Ton N.Y.C. , Locomotive 

B- 222 Ton Penn. K.E. Steam Pacific 

Type Locomotive 
C- 192 Ton Penn. E.E. Steam Atlantic 

Type Locomotive 


/ 


/ 
















v\ 



















100 



200 



600 



700 



300 400 500 

Time Lii_Secoiids 

Fig. 190. — Passenger train spe.ed-time curves. (750 trailing tons on 
Y^ per cent, grade.) 

type. The curves show clearly the great advantages possessed 
by electric locomotives when operating in a service which requires 
a large number of stops. 

A most inspiring and graphic demonstration of the ability of 
the New York Central locomotive, particularly in rapid ac- 
celeration, was the often quoted test carried out in 1904 on the 
New York Central Railroad when electric locomotive No. 6000, 
drawing eight Pullman coaches with a total train weight of 478.5 
tons, after reaching the same speed as the New York Central 
fast express was allowed to attain its maximum speed and was 
found to gain a full train length in the distance of 1 mile. 



ELECTRIC TRACTION ON TRUNK LINES 401 

General Suitability for the Service. — In many respects the 
electric motor is better adapted for railway service than the steam 
engine. The motions of the moving parts are simpler and all 
moving parts can be readily balanced. The weight and volume 
per horse power output are much lower. 

In cold weather the drawbar pull necessary to haul a given 
train at a given speed is greater than in warm weather. Cold 
weather decreases the drawbar pull of the steam locomotive 
because of the increased heat radiation from the boiler and en- 
gines, while the drawbar pull of the electric locomotive, for a 
given temperature of the motor windings, is increased. 

The coefficient of adhesion is higher with electric than it is with 
steam locomotives because the torque of the electric motors is 
uniform and there are no unbalanced forces tending to lift the 
locomotive from the track. 

Steam locomotives must carry their own supplies of fuel and 
water and these supplies must be renewed at frequent intervals. 
Stops for this purpose lower the schedule speeds and tend to 
congest traffic. 

Experience gained in the practical operation of existing electric 
locomotives indicates that they require inspection once in from 
1200 to 2500 miles of operation. To keep steam locomotives in 
equally good condition they must be inspected and cleaned at 
the end of each run 

Service does not decrease the efficiency of an electric loco- 
motive, while on account of the fouling of heating surfaces, the 
efficiency of the steam locomotive may be seriously impaired. 

On the other hand, electric locomotives are still in the develop- 
ment stage, while steam locomotives are quite well standardized. 
The steam locomotive is an independent unit. Its operation is 
in no wise affected by the proximity of other locomotives nor does 
it depend on an outside source for its supply of energy. 

Long continued overloads injure electrical equipment and do 
not seriously affect the life of steam equipment. Electric loco- 
motives designed for operation in connection with one electric 
system cannot usually be operated in connection with a different 
system. Steam locomotives have therefore a much higher degree 
of interchangeability. 

Electrification Increases Real Estate Values. — One of the more 
important by-products of electrification is the great increase in 
the value of the real estate which is covered by the terminal tracks 

26 



402 ELECTRIC RAILWAY ENGINEERING 

in large cities. Office buildings may be constructed over the 
tracks as has been done at New York City. The salvage value 
of such land is very great. Real estate adjoining the right-of-way 
also increases in value on account of the elimination of the smoke 
and the partial abatement of the noise nuisance. 

Cost of Electrification and Operation. — Granted that the 
service can be improved and the capacity of a road increased 
with electric traction as pointed out above, an answer to the 
second question must be found, i.e., ''What will it cost to change 
and to operate and maintain the new system when installed?'' 

The first cost of the change will vary greatly with local con- 
ditions and in any case would probably be prohibitive if under- 
taken for a complete trunk line system at once. Experimenta- 
tion, if necessary at all, should be carried out upon some of the 
less important branches and the electrical rolling stock secured a 
portion at a time. It has even been suggested that as the pur- 
chase of new steam locomotives to replace those worn out or 
considered obsolete is usually treated by steam roads as an 
operation charge and not a charge against capital, the electrical 
rolling stock, or a large portion of it, might be secured in like 
manner and no great capital investment made for this portion 
of the new system. 

As has been pointed out in a preceding chapter, there is a grow- 
ing tendency on the part of railway companies to purchase the 
electrical energy required for the operation of their trains of 
commercial power companies. This is particularly true in the 
West where water power is plentiful and coal is costly. By so 
doing, the first cost of electrification is greatly reduced ; the annual 
costs for energy are usually less and the fact that the energy 
supply is often received from a transmission network insures 
better continuity of service. 

The American Institute of Electrical Engineers was partic- 
ularly fortunate at its 1911 annual convention to have presented 
by the Pennsylvania Railroad through Mr. B. F. Wood, a very 
detailed statement of the first cost and operating expenses of the 
electrification of the West Jersey and Seashore Railroad. While 
the figures for a larger trunk line operating locomotives in place 
of motor car trains would vary somewhat from those applying 
to this road as illustrated in the discussion which follows, the 
costs of this particular electrification which are the first to be 
made public in complete detail are well worthy of careful study. 



ELECTRIC TRACTION ON TRUNK LINES 403 

Tables XL VI and XL VII give total and unit costs of electri- 
fication, while operating expenses are well analyzed in Tables 
XL VIII to LI inclusive. The costs apply to a total of 150 
miles of single track upon which 47- to 52-ton cars are operated 
in trains with two 200 hp. motors per car controlled with the 
multiple unit equipment. The power station is of 8000 kw. 
capacity supplying power to eight substations ranging from 1000 
to 2500 kw. each. The distribution voltage on the third rail 
system is 675 volts direct current. 

Table XLVl. — Cost of Electrification 
Power stations: 

Building, stacks, coal and ash handling machinery. . . $354,000 
Equipment 640,900 

Total $994,900 

Transmission line 241,500 

Substations : 

Buildings .* 72,000 

Equipment 419,560 

Total 491,560 

Third rail 557,636 

Overhead trolley 80,500 

Track bonding 102,659 

Cars 1,135,900 

Car repair and inspection sheds 46,674 

Right-of-way, additional 592,100 

Reconstructing tracks 763,800 

Constructing new tracks 2,071,000 

Terminal facilities and changes at stations 252,400 

Signals and interlocking plants 561,900 

Changing telegraph and adding telephone facilities 105,100 

Fencing right-of-way, cattle guards, etc 88,400 

Miscellaneous items 44,200 

Total $8,130,229 

Table XLVll.^ — Unit Costs of Electrification 

Power station, cost per kw $124 . 36 

Transmission line, cost per mile 3,485.00 

Substations, building and equipment cost per kw . 28 . 90 

Third rail, cost per mile 4,235 . 00 

Overhead trolley, cost per mile 4,120.00 

Track bonding, cost per mile 684 . 50 

Cars, including electrical equipment, each 12,214.00 

^ "Electrical Operation of the West Jersey & Seashore Railroad," by 
B. F. Wood. A. 1. E. E., Vol. XXX. 



404 ELECTRIC RAILWAY ENGINEERING 

Table XLVlll.^ — Power Station Operation and Maintenance Cost 



Year 1910 



Items 



Total Centperkw.hr. 



o 



Boiler room 

Turbine 

Labor \ Electrical 

Supervision janitors and watchmen 
Total operating labor 



Material [ 



Coal 

Water 

Lubricants 

Misc. material 

Misc. charges 

Total operating material . 
Total operation 



Labor < 



Building 

Boiler room 

Turbine 

Auxiliary apparatus 

Electrical 

Piping 

Miscellaneous 

Total maintenance labor. 



Material 



Building 

Boiler room 

Turbine 

Auxiliary apparatus 

Electrical 

Piping 

Miscellaneous 

Total maintenance material 
Total maintenance 



Total labor 

Total material 

Total labor and material station proper . 
Other items charged to station accounts. 

Total 

Net output 

Pounds coal per kw. hr 

Cost of coal per 2000 lb 



$14,742.36 

10,010.81 

1,661.02 

2,756.23 



29,170.42 

102,715.31 
500.00 



2,238.44 
1,700.49 



107,154.24 



136,324.66 

326.29 
1,550.44 
836.11 
844.17 
195.30 
691.94 
187.30 



4,631.55 

146.63 
2,493.23 
1,597.52 
2,066.13 
3,046.44 
383.97 
599 . 06 



10,332.98 



14,964.53 

33,801.97 
117,487.22 
151,289.19 
2,160.60 
153,449.79 
28,312,500 
3.246 
$2,235 



0.052 
0.035 
0.006 
0.010 



0.103 

0.363 
0.002 



0.007 
0.006 



0.378 



0.481 

0.001 
0.005 
0.003 
0.003 
0.001 
0.002 
0.001 



0.016 

0.001 
0.009 
0.006 
0.007 
0.011 
0.001 
0.002 



0.037 



0.053 

0.119 
0.415 
0.534 
0.008 
0.542 



1 "Electrical Operation of the West Jersey & Seashore Railroad," by 
B. F. Wood. A. I. E. E., Vol. XX X. 



ELECTRIC TRACTION ON TRUNK LINES 



405 



Table XLIX 


.1 — Average Cost 


OP Train Operation Per Car M 


ILE 




a 


s 


"o 


rt 


(3 






T3 
















o 


d) <n 




























" -S 


4J 


^ 
















o. 


Yprt 




a 




M 

1 


3 

OQ 






1 




i 


s 


13 


i 






a 


a q; 

s.s- 

o 


o 

11 


If 


i 
1 


a 

V 

S 
a 

H 


Si 

a 

^0, 


1 

o 


Other expe 
Totsi expen 


s 
o 




1909 


0.68 


1.10 


0.25 


4.30 


0.33 


0.88 


1.44 


0.69 


9.67 


9.08 


18.75 


4,107,609 


3.457 


1910 


0.66 


1.01 


0.27 


3.33 


0.43 


0.91 


1.52 


0.67 


8.80 


9.39 


18.19 


4,552,532 


3.518 


1912 


0.96 


1.07 


0.22 


5.10 


0.43 


0.90 


1.61 


0.79 


10.08 


9.95 


20.03 


4,647,236 


3.598 



Table L. — Cost op Transmission System Maintenance 

(Total and average per mile per month) 



Year 


High tension 


Overhead trolley 


Third rail 


Running track 
bonding 


Total 


Per 
mile 


Total 


Per 
mile 


Total 


Per 
mile 


Total 


Per 
mile 


1910 


$3,444.57 


$4.10 


$4,895.16 


$36.70 


$10,864.13 


$6.46 


$2,445.72 


$1.36 


1912 


5,060.67 


7.30 


6,161.03 


64.01 


14,045.73 


9.91 


3,228.84 


1.79 



Table LI. — Cost op Substation Operation and Maintenance 



Year 


Total for eight substations 


Operation 


Maintenance 


Total 


Cost per 
kw. hr. 


Substation output kw. hr., 
675 volts direct current 


1910 
1912 


$20,852.31 
20,953 . 92 


$3,607.30 
2,729.55 


$24,459.61 
23,683.47 


$0.001082 
0.000967 


21,972,300 
24,481,100 



Kahler has estimated the cost of a single-phase electrification 
of 467 miles of steam railroad located in the mountainous 
regions of the West and handling a traffic of 2,814,407,580 ton 
miles annually as follows: 2 

Item 

High tension lines (steel tower), 450 miles $2,250,000 

Trolley and feeder wire : 

3/0 grooved copper trolley, 468 miles at $650 $304,200 

Steel trolley wire, 156 miles at $320 49,920 

2/0 feeder wire, 468 miles at $550 234,000 



588,120 
^ "Electrical Operation of the West Jersey & Seashore Railroad," by 

B. F. Wood. A. 1. E. E., Vol. XXX; and G. E. Review, Nov., 1913. 
2 "Trunk Line Electrification," by C. P. Kahler. A. I. E. E., Vol. XXXll, 

page 1209. 



406 ELECTRIC RAILWAY ENGINEERING 

Overhead construction: 

Bracket arm construction, 420 miles at $1650.. . . 693,000 

Span construction, 92 miles at $2600 239,200 

Steel bridges, 4 miles 36,000 

Section breaks 6,600 

Additional for curved track, 100 miles at $300. . . 30,000 

1,004,800 

Track bonding, 624 miles at $450 280,800 

Substations : 

14 substations, 56,000 kv.a 616,000 

3 portable substations, 6000 kv.a ... (complete) 96,000 



712,000 



Rolling Stock: 

14 motor cars at $18,000 252,000 

10 passenger locomotives at $45,000 450,000 

43 freight locomotives at $50,000 2,150,000 

11 switching locomotives at $35,000 385,000 



3,237,000 



Changing block signals and telegraph, 468 miles. . 561,600 

Engineering and supervision, 5 per cent 431,716 

Contingencies, etc., 10 per cent 905,964 

Total $9,972,000 

Credit for steam equipment : 

140 locomotives $2,520,000 

241 coal cars 241,000 

14 passenger cars 112,000 

Give credit for 70 per cent, of new value $2,873,000 2,012,000 

Net estimate $7,960,000 

Cost per mile of track $17,200 

In order to obtain an idea of the magnitude of the cost of electri- 
fication of the trunk lines of the United States, attention should 
be given to the estimates which have been made by Stillwell and 
Putnam,^ particularly with regard to the effect upon this cost of 
a reduction of frequency to 15 cycles. Their estimate is based 
upon a continuous output of 2,100,000 kw. from all the power 
stations combined. The power station apparatus such as tur- 

i''On Substitution of the Electric Motor for the Steam Locomotive," by 
Lewis B. Stillwell and Henry St. Clair Putnam. A. 1. E. E., Vol. XXVI. 



ELECTRIC TRACTION ON TRUNK LINES 407 

bines, transformers, meters, etc., which would be effected by- 
frequency is estimated at $30 per kw. at 25 cycles, or $33 at 
15 cycles. Substation transformers would be increased one- 
third in first cost, so that the cost of electrical equipment in 
power house and substations would be increased from $70,000,000 
to $80,000,000, with the decrease in frequency. The assumption 
is made, although open to serious question, that one electric 
locomotive costing $25,000 will do the work of two designed 
for steam operation. With this assumption the aggregate 
cost of electric locomotives will be $600,000,000 at 25 cycles. 
The cost of these locomotives would be reduced with the change 
in frequency by possibly $1000 each. Storer places this figure 
at $5000. With the former and more conservative estimate the 
saving with the lower frequency on locomotives is $24,000,000, 
which is more than double the increase in cost of power station 
and substation equipment. This points toward a conservatively 
estimated saving of $14,000,000 if the lower frequency be chosen. 

Going a step farther into these rather astounding estimates, 
the power station equipment for this general electrification figured 
at the low value of $100 per kw. would amount to $210,000,- 
000, with possibly an added $63,000,000 for substations and 
$600,000,000 for locomotives, etc., reaching a grand total esti- 
mated at one and one-half billions of dollars for the entire under- 
taking. 

Upon the other hand, if the figures quoted by Murray^ based 
upon actual observations of maintenance and operation costs 
upon the electrified section of the New York, New Haven & 
Hartford Railroad are given serious consideration, it will be found 
that the above tremendous outlay is not confined to improve- 
ments in service and increased capacity of road alone, but that 
it will return dividends in the form of lowered operating costs and 
maintenance charges as well. For example. Table LI indicates 
the saving in coal per annum measured at the power house of 
the electrified system as compared with that used in the fire 
box of the steam locomotive performing the same schedule. 

This means that the saving in coal alone on a short section of 
but one trunk line will amount to $341,470 per annum due to elec- 
trical operation, while further study of gains in maintenance 
leads to the conclusion that the cost of repairs of the electrical 

^ Discussion by W. S. Murray upon paper, "On the Substitution of the 
Electric Motor for the Steam Locomotive." A. 1. E. E., Vol. XXVI. 



408 ELECTRIC RAILWAY ENGINEERING 

Table Lll. — Saving in Coal Due to Electrification 





Ton miles 
per annum 


Tons coal 

steam 

traction 


Tons coal 
electric 
traction 


Cost coal 

steam 
traction 


Cost coal 
electric 
traction 


Saving of 

elec. over 

steam 


Express 

Express local. . . 
Express freight 


592,240,000 

348,000,000 

2,223,000,000 


57,447 

58,300 

187,844 


29,870 

28,600 

139,010 


1183,830 
186,560 
563,530 


$89,620 

85,800 

417,030 


$94,210 
100,760 
146,500 


Total saving . . . 












$341,470 



equipment will be but one-third or one-fourth that of steam loco- 
motives. These two savings alone when capitalized for all the 
trunk lines of the country will go a great way toward balancing 
the seemingly excessive first cost of electrification estimated 
above. 

The data presented by J. B. Cox in ''The Electrical Operation 
of the Butte, Anaconda & Pacific Railway/' Proceedings of the 
American Institute of Electrical Engineers, November, 1914, 
seems to check Murray's figures fairly well, particularly as re- 
gards the saving in cost of fuel. The Butte, Anaconda & Pacific 
Railway is an ore road and has a route mileage of 25.7 miles and 
a track mileage of 90.5 miles. The traffic, which is very heavy, 
was formerly handled by twenty-seven steam locomotives. It is 
now handled by seventeen 80 ton, 2400 volt direct current electric 
locomotives^ and five steam locomotives. The electric locomo- 
tives operate about 80 per cent, of the total annual locomotive 
mileage. The electrical energy required is purchased of a hydro- 
electric power company which operates a high tension transmis- 
sion network in the vicinity of the railway. Coal for the steam 
locomotives costs $4.25 per ton delivered at the railway company 
bins. The total cost of electrification was 11,201,000. No 
reduction was made for the salvage of the twenty-two steam 
locomotives which were displaced. In the following table the 
operating expenses for 1914 include the expenses of the five 
steam locomotives which are still in service on tracks not yet 
electrified. Presumably still greater economy will be affected 
when the electrification is complete, the operating forces better 
trained and the equipment a little farther removed from the 
experimental stage. 

^ See chapter on Electric Locomotives. 



ELECTRIC TRACTION ON TRUNK LINES 409 

Table LUX. — Operating Expenses of Butte, Anaconda & Pacific Ry. 



Item of operating expense 


Steam, 
1913 


Electric, 
1914 


Decrease 


Per cent, 
decrease 


Fuel and power ... 


315,235.74 

124,787.90 

104,461.18 

29,907.80 

4,953.66 

9,751.44 

5,823.52 


164,508.70 

92,278.08 

71,225.28 

18,638.38 

1,193.70 

4,942 . 32 

4,552.36 


150,727.04 

32,509.82 

33,235.30 

11,269.42 

3,759.96 

4,809.12 

1,271.16 


47.81 


Repairs 


26.05 


Enginemen's wages 

Engine house expenses 

Water 


31.81 
37.68 
75.90 


Lubricants 


49.30 


Other supplies 


21.83 


Total locomotive perform- 
ance . . 


594,921.24 
147,632.30 


357,339.42 
116,486.00 


237,581.82 
31,146.30 


39 93 


Trainmen's wages 


21.10 


Grand total 

Ton miles hauled 


742,553.54 
158,917,720 


473,825.42 
172,855,856 


268,728.12 
13,938,136^ 


36.19 

8 77^ 







^ Increase. 

After subtracting from $268,728.12 a sum necessary to cover 
depreciation charges and distribution system maintenance ex- 
penses, the total net saving with electric operation was S242,- 
299.12 or 20.2 per cent, on the cost of electrification. This net 
saving was made in spite of the fact that 8.77 per cent, more ton 
miles were hauled in 1914 than in 1913. 

On account of the high first cost of electrification, and there- 
fore the high fixed charges, it is evident that it would not pay 
to electrify a road over which the traffic is light. Only a very 
careful study of each particular case will enable an engineer to 
decide whether electrification will justify itself or not. With 
steam motive power, the first cost and fixed charges are low, 
while with the electric motive power the possibility of low 
operating expenses and increase of gross earnings is presented. 

In conclusion it may be said that the greatest objection to 
electrification is the high first cost, and its most important ad- 
vantages are safety, increased capacity of track and economy. 



INDEX 



Acceleration, rates of, 61 
Adhesion, coefficient of, 92 
Adhesive weight, locomotive, 91 
Air brake equipment, 323, 326 
Alternating current control, 314 
Alternating versus direct current 

traction, 369 
Axles, car, 257 

Ballast, 236 

Block signals, 211 

Bonds and bonding, 188 
amalgam, 191 
cast, 191 

compressed terminal, 189 
cross bonding, 195 
soldered and brazed, 189 
testing, 193 
welded, 189, 192 

Brakes, 318 

air brake rigging, 323, 326 
automatic air, 329, 330 
dimensions of brake rigging, 324 
electric, 331 
equipment, 323, 326 
friction disk, 331 
hand brake rigging, 324, 326 
quick action automatic air, 330 
shoes, improper method of hang- 
ing, 322 
shoes, proper method of hang- 
ing, 321 
straight air, 328 
track, 331 

Braking (see also brakes), 64 
energy required for, 84 
forces acting during, 321, 325 
friction of brake shoes, 318 
motors used as generators, 331 
regenerative, 100, 297, 316, 332, 

356, 380 
reversal of motors, 331 
tests, 333 



Butte, 



Anaconda & 
motive, 354 



Pacific loco- 



Cab signals, 229 

Cab underframing, 363 

Cabs, locomotive, 363 

Capacity of transmission line, 158 

Car demand curves, 29 

Car house, design, 336, 341 

equipment, 345 

fire protection, 341 

floors, 343 

heating, 343 

lighting, 343 

location, 336 

offices, and employees' quarters, 
344 

pit construction, 342 

repair shops, 345 

tracks, 337 

transfer table, 340 
Cars, 253 

axles, 257 

bodies, 254 

California type, 269 

city, 266 

double-deck, 269 

elevated and subway, 271 

frames, 254 

freight, 272 

gas electric, 273 

heating, 260 

interurban, 270 

lighting, 259 

lubrication, 257 

motor equipment, 258 

near side, 268 

number and capacity, 22 

pay-as-you-enter, 264 

roofs, 255 

selection, 253 

stepless, 268 

stoiage battery, 272 



411 



412 



INDEX 



Cars, suburban 269 
trucks, 256 
ventilation, 261 
weight of, 49 
wheels, 257 
wiring, 264 
Catenary construction, 117 
Center of gravity of power demands, 

121 
Characteristics, locomotive, 90, 353, 

354, 395 
Characterists of motors, 37, 39, 40, 
41, 283, 284, 285 
direct current, 37, 39, 40, 41, 

284 
single-phase, 283, 285 
Charging current of transmission 

line, 159 
Coasting, 63 

energy consumed in, 84 
Competition, relation to traffic of 

steam roads, 20 
Control, alternating current, 314 
auxiliary contactor equipment, 

304 
bridge transition, 304 
classification, 300 
combined a. c. and d. c, 315 
electro-magnetic, 308 
electro-pneumatic, 309 
high voltage d. c*., 313 
main circuit, 301 
master, 306 
multiple unit, 308 
PK system, 313 
regenerative braking, 316 
rheostatic, 301 
selection, 317 
series parallel, 302 
three-phase, 315 
types, 299 
unit switch, 309 
wiring, a. c, d. c. Fig. 149 
multiple unit, 308 
series parallel, simplified, 303 
unit switch, multiple unit. 
Fig. 147 
simplified, 311 
Cost, a. c. and d. c. installation, com^ 
parative, 382, 383 



Costs, a. c. and d. c. operation 
comparative, 382, 383, 384 

electrification, 402 

fuel saved by electrification, 
408, 409 

locomotive, 365 

power, 167 

power station, 183, 186, 187 
maintenance and operation, 

168 
operation, 404 

roadbed, 235, 251, 252 

signals, 229 

substation, 148 

operation and maintenance, 
122, 405 

train operation, 405 

transmission system mainten- 
ance, 405 
Current collection, 262 
Current time curves, 66, 67, 76, 97, 

98 
Curves, current time, 66, 67, 76, 97, 
98 

distance time, 60, 66, 75, 76 

kilo volt-ampere time, 69 

kilowatt time, 69 

power time, 68, 76 

resistance due to, 58 

speed time, 60, 75, 76, 78, 80, 
81, 82, 97, 98 

speed tractive effort, 395 

service capacity, 399 

substation load, 102, 104 

tonnage rating, 398 

track, measurement of, 57 

Dispatching, telephone, 210 
Dispatcher's control signal, 216 
Distance time curves, 60, 66, 75, 76 
Distribution, city systems. 111 

continuous feeder, 107 

division of current between sub- 
stations, 109 

double catenary, 117 

feeder with infrequent taps, 110 

financial considerations, 112 

high voltage, direct current, 118 

Kelvin's law, 113 

single-phase, 117 



INDEX 



413 



Distribution system, 106, 114 

third rail, 116 

uniformh^ loaded feeders, 112 
Double-deck car, 269 
Drawbar pull, 89 
Drive wheels, locomotive, 89, 362 
Duration of stop, 28 

Economy, comparison of steam en- 
gine and turbine, 170 
Electric locomotives, 346 
Electric traction on trunk lines, 387 

versus steam, 389 
Electrification costs, 382, 384, 402 

systems, 369 
Electrifications, modern prominent, 

388 
Electrolysis, 196 
Elevated and subway cars, 271 
Engine, steam, economy, 170 

specifications, 172 
Energy calculations, 77, 78, 83, 92 . 
of car, 77, 78, 83 
during braking period, 84 
during coasting, 84 
regeneration of, 100, 297, 316, 
332, 356, 380 

Feeders with infrequent taps, 110 
Field control of motors, 276 
Freight cars, 272 

train resistance, 95 
Frequency effect of change on 

motors, 288 
Friction, bearing and rolling, 50 

coefficient for brake shoes 318 

Gas electric car, 273 
Gear ratio, 46 

Generators, alternating current, 174, 
177, 178 
direct current, 172, 174 
Grades, 56 

effect on drawbar pull, 396 
ruling, 57 

Income, gross, 21 
Induction motor, 282, 286 
Inertia of wheels and armature, 
rotative, 53 



Kelvin's Law, 113 
Kilovolt-ampere time curves, 69 
Kilowatt time curves, 69 



Lighting, car, 259 

Lightning arrester, clectroh^tic, 143 

Lightning protection, 142 

Load factor, 105 

Locomotives, electric, 346, 348 

adhesive weight, 91 

Butte, Anaconda & Pacific, 354 

cab underframing, 363 

cabs, 363 

capacity determinations, 96 

characteristics, 90, 353, 354, 395 

coefficient of adhesion, 92 

C. M. & P. S. d. c, 355 

costs, 365 

current time curves, 97, 98 

data, 348, 349 

design requirements, 358 

drawbar pull, 89 

drive wheels, 362 

interurban, 355 

mercury vapor rectifier, 357 

motor mountings, 358 

New York Central, 350 

N. Y., N. H. & H., 351 

Pennsylvania, 352 

power time curves, 97, 98 

ratings, 347 

riding qualities, 364 

service capacities, 397 

speed time curves, 97, 98 

split -phase, 356 

tonnage rating, 93 

train haulage, 89 

train resistance, 90, 91 

transmissions, 358 

weights, 91, 362 

Maximum traction trucks, 258 

M. C. B. trucks, 258 

Mercury vapor rectifier locomotive, 

357 
Motor equipment, 258 
Motor generator, starting, 130 

versus synchronous converter, 

134 



414 



INDEX 



Motors, adaptation of d. c. series to 

a. c, 278 
characteristics, d. c, 37, 39, 40, 

41, 284 
characteristics of single-phase, 

283, 285 
commutating pole, 276 
design, 288 
direct current, 275 
field control, 276 
frequency, effect of change on, 

288 
induction, 282, 286 
operation of single-phase on 

d. c, 284 
pressed steel, 277 
rating, 290 
repulsion, 285 
selection, 241, 292, 295 
single-phase, 277, 283 
temperature rise, 291 
tests, 44, 46, 293 
torque, determination of, 43 
vector diagram of single-phase, 

279 

Nearside cars, 268 

New York Central locomotive, 350 

N. Y., N. H. & H. locomotive, 351 

Offices and employees' quarters, 344 

Pantograph trolley, 262 
Passengers standing by preference, 

30 
Pavement, 249 
Pay-as-you-enter cars, 264 
Population, effect upon traffic, 13 

growth of, 14 
Power, cost of, 167 

demand, center of gravity of, 
121 
Power station, 162 

arrangement of equipment, 183 

capacity, 165 

cost, 183, 186, 187 

design, 165 

double-decked, 185 

elevation of, 169 

elevation of steam turbine, 184 



Power station, exciters, 180 

fuel saving due to electrification, 
408 

location, 162 

maintenance and operation cost, 
168 

operation, 404 

plan of gas engine, 182 

prime movers, 167 

switchboard, 180 

transformers, 179 
Power time curves, 68, 76, 97, 98 



Rail joints, 244 

thermit, 191 

welded, 191, 192 
Rails, 238 

analysis, 243 

corrugation, 245 

joints, 244 
Rating of motors, 290 
E.eactance of transmission line, 154 
Regenerative braking, 100, 297, 316, 

332, 356, 380 
Regulation, transmission line, 155 
Repair shops, 345 
Repulsion motor, 285 
Resistance, air, 51 

due to curves, 58 

formula for train, 53 

third rail and track, 108 

train, 53 

transmission line, 154 
Riding habit, 19 
Right-of-way, 231 
Rolling stock (see cars), 253, 346 

d. c. versus a. c, 380 
Ruling grade, 57 

Schedules, train, 31 

Selection of motors, 241, 292, 295 

Signal and dispatching systems, 209 

alternating current, 222 

aspects, 213 

block, 211 

cab, 229 

controlled manual block, 216 

cost, 229 

dispatcher's control, 216 



INDEX 



415 



Signal and dispatching systems for 
a. c. roads, 224 

intermittent control, 218 

manual controlled block, 215 

Simmen, 216 

single-track, 226 

staff sj^stem, 209 

steam railroad, 220 

systems, 210 

track circuit, 221 

U. S. signal, 219 
Single-phase motors, 277, 283 
Speed time curves, 59 

straight line, 80 
Split-phase system, 356, 370 
Standardization of electrified roads, 

379 
Standing by preference, 30 
Statistics, 15 
Steam roads, relation of competition 

to traffic of, 20 
Stop, duration of, 28 
Storage battery, auxiliary, 138 

car, 272 
Substation, arrangement of appara- 
tus, 139 

cost, 148 

demand, 102, 104 

design, 124 

division of current between, 109 

financial considerations of, 112 

high voltage, direct current, 145 

lightning protection, 142 

load curve, 104 

location, 120 

operating costs, 122 

operation and maintenance cost, 
405 

outdoor, 146 

portable, 144 

single-phase, 146 

switchboard, 135 

typical elevation, 139, 140 

wiring, 139, 141 
Switchboard, power station, 184 

substation, 135 
Synchronous converter, comparative 
ratings, 129 

compounding, 126 

efficiency, 126 



Synchronous converter, starting, 130 
versus motor generator, 134 
voltage ratio, 126 

Tests, braking, 333 

motor, prony brake, 44 
pumping, back, 44 
used as generator, 46 
rail bonds, 193 
Thermit rail joints, 191 
Third rail, construction, 116 
distribution, 116 
resistance of, with track, 108 
shoe, 263 
Ties, 237 

Track ballast, 236 
car house, 337 
construction, 247 
curves, measurement of, 57 
estimates, 235, 251, 252 
pavement, 249 
rails, 238 
special work, 250 
third rail and, resistance of, 108 
ties, 237 

typical construction, 234 
Traction, electric, growth in U. S., 11 
electric on trunk lines, 387 
alternating versus direct cur- 
rent, 369 
cost, 382, 383 
fuel saving, 408 
locomotives, 346, 348 
operating cost of a. c. and d. c, 

382 
power station operation, 404 
standardization, 379 
substation operation and 

maintenance cost, 405 
train operation cost, 405 
transmission system, mainte- 
nance, 405 
Tractive effort, 39 

consumed in rotating parts, 56 
Traffic, effect of population upon, 13 
of steam roads, relation of com- 
petition to, 20, 21 
statistics, 15 
Train operating costs, 405 
Train schedules, 31 



416 



INDEX 



Transformers, 132 

connections, 127, 129, 130, 
132, 133 

power station, 179 

substation, 132 
Transmission line, 149 

capacity, 158 

charging current, 159 

electrical calculations, 152 

maintenance, 405 

mechanical strength, 151 

reactance, 154 

regulation, 155 

resistance, 154 

vector diagram, 155, 160 

voltage determination, 155 



Trucks, 258, 363 
131, Trunk lines, electric traction upon, 
387 
Turbine, steam, economy, 170 
specifications, 171 

Welded rail joints, 191, 192 
Wiring, a. c, d. c. control. Fig. 149 
car, 264 

multiple unit, 308 
series parallel, simplified, 303 
substation, 139, 141 

diagram, 141 
unit switch, multiple unit, Fig. 
147 
simplified, 311 







iO 



00 



16 






03 



20 



21 



22 



23 



24 



25 



•'liinliml'"'i""l"nlin'l"'iliinliiiiliiiilini 



mi 



CD 



5^ 



05 >i^ ?W' 



CD H 



CD 5' 






